Handbook of Meat,Poultry and SeafoodQualityEditorLeo M. L. NolletAssociate EditorsTerri BoylstonFeng ChenPatti C. CogginsMaria Beatriz GloriaGrethe HyldigChris R. KerthLisa H. McKeeY. H. HuiBlackwellPublishing
Editor, Leo M. L. Nollett, PhD, is Professor ofBiotechnology at Hogeschool Gent, Ghent, Belgium.He is the author and coauthor of numerous articles,abstracts, and presentations, and books. His researchinterests include food analysis techniques, HPLC, andenvironmental analysis techniques. Dr. Nollet hadedited and/or authored six books on analyticalmethodologies for food, drinking water, and environ-mental chemicals.Associate Editors include: Terri Boylston, PhD, IowaState University; Feng Chen, PhD, ClemsonUniversity; Patti C. Coggins, PhD, Mississippi StateUniversity; Maria Beatriz Gloria, PhD, UniversidadeFederal de Minas Gerais, Belo Horizonte, Brazil;Grethe Hyldig, PhD, Denmark Ministry of Food,Agriculture & Fisheries, Lyngby, Denmark; Chris R.Kerth, PhD,Auburn University; Lisa H. McKee, PhD,New Mexico State University; and Y. H. Hui, PhD,Food Industry Consultant,West Sacramento, CA.02007 Blackwell PublishingAll rights reservedBlackwell Publishing Professional2121 StateAvenue,Ames, Iowa 50014, USAOrders: 1-800-862-6657Office: 1-515-292-0140Web site: www.blackwellprofessional.comBlackwell Publishing Ltd9600 Garsington Road, Oxford OX4 2DQ, UKTel.: +44 (0)1865 776868Blackwell PublishingAsia550 Swanston Street, Carlton,Victoria 3053,AustraliaTel.: +61 (0)3 8359 1011Authorization to photocopy items for internal or per-Fax: 1-515-292-3348sonal use, or the internal or personal use of specificclients, is granted by Blackwell Publishing, providedthat the base fee is paid directly to the CopyrightClearance Center, 222 Rosewood Drive, Danvers,MA 01923. For those organizations that have beengranted a photocopy license by CCC, a separate sys-tem of payments has been arranged. The fee codes forusers of the Transactional Reporting Service areISBN-13: 978-0-8138-2446-8/2007.First edition, 2007Library of Congress Cataloging-in-Publication DataHandbook of meat, poultry and seafood quality / LeoM. L. Nollet, editor ;associate editors, Terri Boylston. . . [et al.].p. cm.Includes index.ISBN-13: 978-0-8138-2446-8 (alk. paper)ISBN-10: 0-8138-2446-X (alk. paper)1.Meat-Quality-Handbooks, manuals, etc.2. Poultry-Quality-Handbooks, manuals, etc.3. Seafood-Quality-Handbooks, manuals, etc.I. Nollet, Leo M. L., 1948- 11. Boylston, Terri.TX556.M4H36 2007363.19’29-dc222006022988The last digit is the print number: 9 8 7 6 5 4 3 2 1iv
ContentsList of Contributors, ixPreface, xvPart I. General Food Quality Factors1. Factors Affecting Food Quality: A Primer 32.YH. HuiHazard Analysis and Critical Control Pointsand Muscle Food Safety in the United StatesYH. Hui7Part 11. Sensory Attributes of Muscle Foods22.214.171.124.7.8.History, Background, and Objectives of Sensory Evaluationin Muscle Foods 15M. W SchillingChemical and Biochemical Aspects of Color in Muscle FoodsJ. A.Pkrez-Alvarezand J. Fernhndez-LbpezSensory: Human Biology and PhysiologyM.A.Da Silva and F CendesSensory Methodology of Muscle FoodsI? C. CogginsObjective Methods of Sensory AnalysisJ. L. MontgomeryAttributes of Muscle Foods: Color, Texture, FlavorI? C. Coggins2545617189Part 111. Flavors9. Sensory Characterization 101K. Bett-Garber10. Chemical Characterization 111N. C. Da Costa and S. Eri11. Chemistry, Technology, and Safety of Synthetic FlavorsR. K. Singh and E. Singh12. Process Flavors 151H. H. Baek13. Savory Flavors 163C. Cerny127V
Contentsvi126.96.36.199.188.8.131.52.22.Natural Flavors 183H. KumagaiWood Smoke Flavor 201K. R. CadwalladerBlended Flavors 211S.X Ma, Z. B.Xiao, andl? ChenOff Flavors and Rancidity in FoodsR. B. Pegg andl? ShahidiLand Animal Products 2297: BoylstonMarine Animal and Plant ProductsN. Narain and M. L. NunesMaillard Reaction in Flavor Generation 259M. J? Romero and C. HoTraditional Laboratory Methods 275E. MehinagicRecent Developments in Flavor MeasurementsJ-L. Le Qu6r6217243293Part IV. Beef Quality23. Sensory Evaluation of Beef Flavor 31124. Beef Quality and Tainting 32725. Microbiological and Sensory Properties of Beef 33326. Quality Measurements in Beef 34127. Shelf Life of Meats 35728.R. K. MillerJ. M. MartinJ. ThomasR. S. ChamulR. S. ChamulPackaging and Freezing of Beef as Related to SensoryProperties 369R. WRogersPart V. Pork Quality29. Fresh and Frozen Pork Color 37730.D. H. KropfMicrobiological and Sensory Properties of Fresh and Frozen PorkProducts 395L. McKee31. PorkTaint 405WB. Mike132. Shelf Life of Fresh and Frozen Pork 417M.A. CarrPart VI. Poultry Quality33. General Attributes of Fresh and Frozen Poultry Meat 42934. Poultry Meat Flavor 439L. McKeeI? L. Dawson and N. Spineli
Contents vii35. Color of Fresh and Frozen Poultry 45536. Shelf Life of Fresh and Frozen Poultry 46737. Packaging of Fresh and Frozen Poultry 47538.A. Totosaus,M. L. Pkrez-Chabela, and I. GuerreroM. L. Pkrez-ChabelaA. Totosausand J? KuriMicrobiological and Sensory Properties of Freshand Frozen Poultry 487L. McKeePart VII. Seafood Quality184.108.40.206.43.44.Fish and SensoryAnalysis in the Fish ChainG. Hyldig, E. Larsen, and D. Green-PetersenSensory Profiling of Fish, Fish Product, and ShellfishG. HyldigQuality Index Methods 529G. Hyldig,A.Bremnec E. Martinsddttic and R. SchelvisTexture of Fish, Fish Products, and ShellfishG. Hyldig and D. NielsenPerception of Sensory Quality of Wild and Farmed Fish by Experts,Consumers, and Chefs or Cooks in the Restaurant SectorG. B. Olsson, M. Carlehog, M. Heide, andJ. LutenQuality of Frozen Fish 577J. Nielsen and F Jessen499511549563Appendix. Standards for Meat, Poultry and Seafoodin the United States 589YH. HuiIndex, 695
List of ContributorsJosCAngel PCrez-Alvarez(4)Universidad Miguel HernandezEscuela PolitCcnica Superior de OrihuelaDepartamento de TecnologiaAgroalimentariaCamino a Beniel s/n. (03313)Desamparados,Orihuela (Alicante) EspaiiaEmail:firstname.lastname@example.orgHyung Hee Baek (12)Associate ProfessorDepartment of Food EngineeringDankook UniversitySan 29Anseo-dong, Cheonan 330-714, KoreaEmail: email@example.comKaren L. Bett-Garber (9)Research Food TechnologistSouthern Regional Research CenterAgricultural Research ServiceU.S. Department of Agriculture1100 Robert E. Lee BoulevardNew Orleans, LA 70124 USAPhone: 504-286-4459Fax: 504-286-4419Email: firstname.lastname@example.orgTerri Boylston (Associate Editor, 18)Associate ProfessorDepartment of Food Science and Human NutritionIowa State University2547 Food Sciences BuildingAmes, IA 50011USAPhone: 515-294-0077Fax: 515-294-8181Email: email@example.comAllan Bremner (41)ProfessorAllan Bremner and Associates21Carrock CountMount CoolumQueensland 4573,AustraliaE-mail: bremquall @optusnet.com.auKeith R. Cadwallader (15)Department of Food Science and Human NutritionUniversity of Illinois1302W. PennsylvaniaAve.Urbana, IL 61801 USAPhone: 217-333-5803Fax: 217-333-1875Email: firstname.lastname@example.orgMats Carlehog (43)Head of Sensory LaboratoryEngineerNorwegian Institute of Fisheries and AquacultureResearchMuninbakken 9-13, Breivika, Box 6122, NO-9291Tromsn, NorwayPhone: 4777629043Fax: 4777629100E-mail: email@example.comMandy A. Carr (32)Assistant ProfessorAngelo StateUniversityASU Station #lo888SanAngelo, Texas 76909 USAPhone: 325-942-2027Fax: 325-942-2183Email: firstname.lastname@example.org
XFernando Cendes (5)Department of NeurologyCampinas State University (UNICAMP)Cidade UniversitiriaCampinas, SP, Brazil 13083-970Email: email@example.comChristoph Cerny (13)Firmenich SARue de la Bergbre 7P.O. Box 148CH-1217Meyrin 2Geneva, SwitzerlandPhone: 41227802705Fax: 41227802734Email: firstname.lastname@example.orgRoberto S. Chamul(26,27)California State University5151 State University Dr.Los Angeles, CA 90032 USAEmail: email@example.comFeng Chen (Associate Editor, 16)Assistant ProfessorContributorsDepartment of Food Science and Human NutritionClemson UniversityClemson, South Carolina 29634 USAPhone: 864-656-5702Fax: 864-656-0331Email: firstname.lastname@example.orgPatti C. Coggins (Associate Editor, 6, 8)Assistant Research ProfessorDepartment of Food Science and TechnologyDirector, Garrison Sensory Evaluation LaboratoryMississippi State UniversityMail Stop 9805Stone Boulevard, Herzer BuildingMississippi State, MS 39762 USAPhone: 662-325-4002Fax: 662-325-8728Email: email@example.comNeil Da Costa (10)International Flavors & Fragrances, Inc.1515 State Highway 36Union Beach, NJ 07735 USAPhone: 732-335-2110Fax: 732-335-2350Email: firstname.lastname@example.orgMaria Aparecida A.P. Da Silva (5)Food and Nutrition DepartmentCampinas State University (UNICAMP)P.O. Box 6121Campinas, SP, Brazil 13083-862Phone: 551937884074Fax: 551937884060Email: email@example.comPaul L. Dawson (34)Professor of Food Science and Human NutritionFood Science and Human Nutrition DepartmentClemson UniversityClemson, SC 29634-0316USAPhone: 864-656-1138Fax: 864-656-0331Email: firstname.lastname@example.orgSanja Eri (10)Mastertaste546 US Route 46Teterboro,NJ 07608 USAPhone: 201-641-8200Maria Beatriz Abreu G16ria (Associate Editor)Departamento de AlimentosLaboratbrio 2091 Bloco 3Faculdade de FarmiciaUniversidade Federal de Minas GeraisAv.Antonio Carlos 6627Belo Horizonte, MG, 31270-901Phone: 031-3499-6911Fax: 031-3499-6989Email: email@example.comDitte Green-Petersen (39)Research AssistantDanish Institute for Fisheries ResearchDepartment of Seafood ResearchTechnicalUniversity of DenmarkSdtofts Plads, Building 221DK-2800 Kgs. Lyngby, DenmarkPhone: 4545254905Fax: 4545884774Email: Dgr@difres.dkIsabel Guerrero (35)Departamento de BiotecnologiaUniversidad Autonoma Metropolitana - IztapalapaApartado Postal 55-535, C.P. 09340, Mexico D.F.,Mexico
Contributors xiPhone: 5257244717 or 5257244726Fax: 5257244712Email: firstname.lastname@example.orgMorten Heide (43)ScientistNorwegian Institute of Fisheries and AquacultureResearchMuninbakken 9-13, Breivika, Box 6122, NO-9291Tromsn, NorwayPhone: 4777629097Fax: 4777629100Email: email@example.comChi-Tang Ho (20)Department of Food Science, Cook CollegeRutgers, The State University of New Jersey65 Dudley RoadNew Brunswick, NJ 08901-8520USAPhone: 7329329611Fax: 7329326776Email: firstname.lastname@example.orgY. H. Hui (Associate Editor, 1, 2, Appendix)Senior ScientistScience Technology SystemP.O. Box 1374West Sacramento, CA 95691USAPhone: 916-372-2655Fax: 916-372-2690Email:YHHUI@AOL.COMGrethe Hyldig (Associate Editor, 39, 40,41,42)Senior Research ScientistDanish Institute for Fisheries ResearchDepartment of Seafood ResearchTechnical University of DenmarkSdtofts Plads, Building 221DK-2800 Kgs. Lyngby, DenmarkPhone: 4545252545Fax: 4545884774Email: email@example.comFlemming Jessen (44)Senior Research ScientistDanish Institute for Fisheries ResearchDepartment of Seafood ResearchTechnical University of DenmarkSdtofts Plads, Building 221DK-2800 Kgs. Lyngby, DenmarkPhone: 4545252549Fax: 4545884774Email: firstname.lastname@example.orgChris R. Kerth (Associate Editor)Auburn UniversityAnimal Sciences Department209 Upchurch HallAuburn,AL 36849 USAPhone: 334-844-1503Fax: 334-844-1519Email: email@example.comDonald H. Kropf (29)Kansas StateUniversityProfessor,Animal Sciences & Industry247 Weber Hall, Manhattan, KS 66506Phone: 785-532-1235Fax: 785-532-7059Email: firstname.lastname@example.orgHitomi Kumagai (14)Associate ProfessorDepartment ofAgricultural and BiologicalChemistryCollege of Bioresource SciencesNihon University1866 KameinoFujisawa-shi 252-8510,JapanPhone: 81 466 84 3946Fax: 81 466 84 3946Email: email@example.comV. Kuri (37)Food and Nutrition, School of Biological SciencesUniversity of Plymouth, Drake Circus, Plymouth,Devon PL4 8AA, United KingdomPhone: 4401752232900Phone (direct): 4401752238315Fax: 441752232970Email: firstname.lastname@example.orgErling Larsen (39)ChiefAdvisory ScientistDanish Institute for Fisheries ResearchDepartment of Seafood ResearchTechnical University of DenmarkSdtofts Plads, Building 221DK-2800 Kgs. Lyngby, DenmarkPhone: 4545252546Fax: 4545884774Email: email@example.com
xii ContributorsJean-Luc Le QuCrC (22)Institut National de la RechercheAgronomique(INRA) Phone: 3545308600Unit6 Mixte de Recherche sur lesAr6mes (UMRA)Icelandic Fisheries LaboratoriesSkulagata 4 IS-101 ReykjavikFax: 354530860117,rue SullyF-21065 Dijon, FranceEmail: firstname.lastname@example.orgJuana Fernindez-Lbpez (4)Universidad Miguel HernandezEscuela PolitCcnica Superior de OrihuelaDepartamento de TecnologiaAgroalimentariaCamino a Beniel s/n. (03313)Desamparados,Orihuela (Alicante) EspaiiaPhone: 3466749656Fax: 3466749609 or 3466749619Email:j .email@example.com orjuana.fernandezaaccesosis.esJoop Luten (43)EU Business DeveloperNorwegian Institute of Fisheries and AquacultureResearchMuninbakken 9-13Breivika, Box 6122, NO-9291Tromsn, NorwayPhone: 4777629078Fax: 4777629100Email:firstname.lastname@example.orgSheng X. Ma (16)International Flavors & Fragrances (China) Ltd.Shanghai, ChinaManager of Flavor Technology (Greater China)Phone: 862162898802Fax: 862162485730Email: email@example.comJames M. Martin (24)Assistant Professor, Department of Animal andDairy Sciences and Food Science,Nutrition andHealth PromotionMississippi State UniversityBox 9815Mississippi State, MS 39762 USAPhone: 662-325-2959Fax: 662-325-8873Email:firstname.lastname@example.orgEmilia Martinsdbttir (41)Head of DepartmentR&D DivisiodConsumer and Food SafetyEmail: email@example.comLisa McKee (Associate Editor, 30, 33, 38)Professor, Human Nutrition and Food ScienceDepartment of Family and Consumer SciencesNew Mexico State UniversityP.O. Box 3003, MSC 3470Las Cruces, NM 88003 USAPhone: 505-646-1182Fax: 505-646-1889Email: firstname.lastname@example.orgEmira Mehinagic (21)Laboratory GRAPPE, ESAAngers & Laboratory of Biochemistry,ENITIAANantes, FrancePhone: 33 2 41 23 55 55Email: email@example.comWilliam Benjy Mike1 (31)Professor and HeadFood Science,Nutrition, and Health PromotionDirector, Food Science InstituteMississippi State UniversityP.O. Box 9805Mississippi State, MS 39762 USAPhone: 662-325-5508Fax: 662-325-8728Email: firstname.lastname@example.orgRhonda K. Miller (23)ProfessorMeat Science SectionDepartment ofAnimal ScienceTexas A&M UniversityCollege Station, TX 77843-2471 USAPhone: 979-845-3901Fax: 979-862-3475Email: email@example.comJayden L. Montgomery (7)Intervet, Inc.P.O. Box 1883Millsboro, DE 19966USAPhone: 302-933-4032Fax: 302-934-4209Email:firstname.lastname@example.org
Contributors...XlllNarendra Narain (19)Departamento de Engenharia QuimicaCentro de CiCnciasExatas e TecnologiaUniversidade Federal do Sergipe, CidadeUniversitiria, Jardim Rosa Elze49100-000, SZo CristbvZo, SE, BrazilEmail: email@example.com ornarendra,firstname.lastname@example.orgDurita Nielsen (42)Research ScientistNorth Carolina State UniversityCenter for Marine Sciences and TechnologySeafood Laboratory303 College CircleMorehead City, NC 28557 USAPhone: 12522226301Fax: 12522226334Email: email@example.comJette Nielsen (44)Research CoordinatorDanish Institute for Fisheries ResearchDepartment of Seafood ResearchTechnical University of DenmarkSdtofts Plads, Building 221DK-2800 Kgs. Lyngby, DenmarkPhone: 4545252550Fax: 4545884774Email:firstname.lastname@example.orgLeo M. L. Nollet (Editor)Hogeschool GentDepartment of Engineering SciencesSchoonmeersstraat 52B9000 Gent, BelgiumPhone: 003292424242Fax: 003292438777Email: email@example.comMaria L6cia Nunes (19)FundaqZoNficleo de Tecnologia Industrial do CeariRua Prof. R8mulo Proenqa, S/NPARTEC, NUTEC, Campus do PIC160451970, Fortaleza, CE, BrazilEmail:firstname.lastname@example.orgGunn Berit Olsson (43)Senior ScientistNorwegian Institute of Fisheries andAquacultureResearchMuninbakken 9-13, BreivikaBox 6122, NO-9291Tromsn, NorwayPhone: 4777629071Fax: 4777629100Email: email@example.comRonald B. Pegg (17)Department of Food Science and TechnologyThe University of GeorgiaAthens, GA 30602-7610 USAPhone: 706-542-1099Fax: 706-542-1050Email: firstname.lastname@example.orgMaria de Lourdes PCrez-Chabela (35, 36)Biotechnology DepartmentUniversidad Autonoma Metropolitana IztapalapaAv San Rafael Atlixo #186Col. Vicentina, Distrito FederalMexico City 09270, MCxicoPhone: (55) 58 04 47 17,58 04 47 26Fax: (55) 58 04 47 12Email: email@example.comRobert W. Rogers (28)Director, Food Science InstituteMississippi State UniversityBox 9804Mississippi State, MS 39762 USAPhone: 662-325-2802Fax: 662-325-8873Email: RROGERS@ADS.MSSTATE.EDUMarissa Villafuerte Romero (20)Department of Food Science, Cook CollegeRutgers, The State University of New Jersey65 Dudley RoadNew Brunswick, NJ 08901-8520 USARian Schelvis (41)Netherlands Institute for Fisheries ResearchP.O. Box 68NL-1970 AB IJmuiden, The NetherlandsPhone: 310255564604Fax: 310255564644Email: Rian.Schelvis@WUR.nlM. W. Schilling (3)Mississippi State UniversityBox 9805Food Science and Technology DepartmentMississippi State, MS 39762 USAEmail: firstname.lastname@example.org
xiv ContributorsFereidoon Shahidi (17)Department of BiochemistryMemorial University of NewfoundlandSt. John’s, NLAlB 3x9Phone: 7097378552Fax: 7097374000Email: email@example.comEpal Singh (11)Department of Food Science & TechnologyThe University of GeorgiaAthens, GA 30602 USAPhone: 7065422286Fax: 7065421050Rakesh K. Singh (11)Department of Food Science & TechnologyThe University of GeorgiaAthens, GA 30602 USAPhone: 7065422286Fax: 7065421050Email:nsinghauga.eduNick Spineli (34)Chief Executive ChefKraft Foods, Chicago, IL USAJack Thomas (25)Microbiology of Fresh and Frozen BeefDepartment ofAnimal and Range SciencesP.O. Box 30003, MSC 31New Mexico State UniversityLas Cruces, NM 88003-8003 USAPhone: 505-646-1943Fax: 505-646-5441Email:firstname.lastname@example.orgAlfonso Totosaus (35, 37)Food Science Lab, Tecnolbgico de EstudiosSuperiores de Ecatepec, Av. Tecnolbgico sln,Ecatepec 55210, Estado de MCxico,MCxicoPhone: +52 (55) 5710 4560Fax: +52 (55)Email: email@example.comZuo Bin Xiao (16)ProfessorDepartment of Food Technology and BiologicalScienceShanghai Institute ofApplied TechnologyShanghai, China 200233
PrefaceThe quality of a food is defined from two perspec-tives-scientific status and consumer preferences.Scientific factors affecting the quality of a foodinclude: composition, spoilage, colorants, additives,nutrients, flavorants, functional ingredients (affect-ing health), contamination, general safety, etc.Consumer preferences are linked directly to thehuman senses-sight, touch, smell, taste, andmouthfeel. Visual factors refer to color, moisture,overall appearance, etc. Tactile factors refer to slim-iness, elasticity, softness, hardness, etc. Factorsresponsible for taste and smell cover many specificchemicals. Mouthfeel refers to texture, softness, ten-derness, chewy sensation, and so on. In the last 10years or so, food quality has been defined by mostprofessionals to include “health” and “safety.” Thenutrition and safety of foods has always been impor-tant, especially since the seventies. The word“health” now includes manipulating certain chemi-cal components in food to increase food’s positiveimpact on our health. “Safety” now refers to a wholespectrum of new legal or recommended require-ments for both fresh and processed foods. Theserequirements are designed to exclude or preventundesirable agents (biological, chemical, physical,environmental, and extraneous) in our foods.For ease of reference, we can consider that thequality of a food is the composite picture of manyfactors. In the last five to ten years, many profes-sional reference books have become available thatexplore the relationship between such factors andfood quality. This book discusses the quality factorsof muscle foods (meat, poultry, and seafood). Eachprofessional reference treatise has its characteristicsand the users determine which one best suits theirpurpose. From that perspective, we will describe themajor features of our book.This book provides an initial discussion of basicscientific factors responsible for the quality of mus-cle foods, with a specific emphasis on sensory attrib-utes and flavors. The remaining sections discuss fac-tors affecting the quality of beef, pork, poultry, andseafood. Under each muscle food, some or all of thefollowing factors affecting the quality will be dis-cussed-additives, aroma, color, contaminants, fla-vors, microbiology, moisture, mouthfeel, nutrition,packaging, safety, sensory attributes, shelf-life, sta-bility,tainting, texture, and water-activity.Each mus-cle food discussedmay be fresh, frozen, or processed.This work is the result of the combined efforts ofmore than 60 professionals from industry, govern-ment, and academia worldwide. They representmore than 16 countries with diverse expertise andbackground in the quality of muscle foods. An inter-national editorial team of 9 members from fourcountries led these experts. Each contributor or edi-tor was responsible for researching and reviewingsubjects of immense depth, breadth, and complexity.Care and attention were paramount to ensure techni-cal accuracy for each topic. It is our sincere hopeand expectation that it will serve as an essential ref-erence on the quality of muscle foods for all profes-sionals in government, industry, and academia.The editorial team wishes to thank all the contrib-utors for sharing their expertise throughout ourjour-ney. We also thank the reviewers for giving theirvaluable comments on how to improve the contentsof each chapter. All these professionals are the oneswho made this book possible. We trust that you willbenefit from the fruits of their labor.xv
xvi PrefaceThis book is relevant to many professionals inindustry, government, and academia and will bemost appreciated by the following users:We know firsthand how hard it is to develop the con-tent of a book. However, we believe that the produc-tion of a professional book of this nature is evenAll libraries.Research units in government, industry, andacademia specializing in one or more foodquality factors (color, flavor, microbiology,packaging, sensory attributes, and so on).Academic institutions: food science, foodtechnology, food engineering, animal science,poultry science, cereal science, marine science,etc.Food industries of commodities covered.Individuals with expertise in any of the foodquality factors discussed in the book.more difficult.We thank the editorial and productionteam at Blackwell, Inc. for their time, effort, advice,and expertise. You are the best judge of the qualityof this book.L. M. L. NolletT. BoylstonF. ChenP. C. CogginsM. B. GloriaG. HyldigC. R. KerthL. McKeeY. H. Hui
4 Part I: General Food Quality Factorsconsider a quality food as one with high nutritionalvalue. Some salient points follow:cleotides (purine derivatives), organic acids (lacticacid), and inorganic salts (Na, K, Cl).1.2.3.FIMeat and poultry are nutritious because of theirhigh source of protein, vitamins, and minerals.The high content of fat and cholesterol in landmuscle foods is undesirable. Thus, “lean”is in.Fish and shellfish are an important part of ahealthy diet. Fish and shellfish contain high-quality protein and other essential nutrients, arelow in saturated fat, and contain omega-3 fattyacids. A well-balanced diet that includes a vari-ety of fish and shellfish can contribute to hearthealth and children’s proper growth and devel-opment.>AVORSAND AROMAOne major reason, among many, that we like to eatis because food tastes good, which equates to flavorand aroma. Extensive research over the past 25 to 30years has identified more than 1,000 flavor com-pounds in meats. However, a single compound orgroup of compounds responsible for “meaty flavor”has not and perhaps never will be identified due tothe overall complexity of meat flavor. Meat flavor isdependent on the pool of flavor precursors in themeat tissue and the chemical reactions that occurduring processing. Processing and subsequent stor-age contribute to the development of the characteris-tic flavors of meats. Because the precise flavor pre-cursors vary between and within species,beef, pork,lamb, and poultry each have distinctive flavor char-acteristics. The quality of meat and poultry is to alarge extent defined by its flavor and aroma.In general, fresh saltwater fish are almost odorlessbecause they contain a small quantity of volatileswhile freshwater fish give off pyrrolidine and otherearthy-odor compounds.The compounds responsible for the developmentof flavor during seafood cooking can be classified intwo groups. One, which represents the pleasant cu-cumbedgreen, almondnutty,and potato aroma notes,consists of highly volatile, low molecular weightcompounds belonging to various chemical classessuch as aldehydes, ketones, alcohols, esters, nitrogen,Biogenic amines are nitrogen-containing com-pounds, which are present at very low levels in freshfish. However, during storage and deterioration, bio-genic amines can be produced by amino acid decar-boxylation from bacterial enzymes. Among biogenicamines formed, putrescine and cadaverine have a pu-trid flavor while histamine and phenylethylaminehave a pungent and fishy flavor, respectively. Bio-genic amines are thermally stable and, therefore, havebeen used as indices to determine fish freshness.Volatile amines such as trimethylamine (TMA) or di-methylamine (DMA) are formed from trimethyl-amine oxide (TMAO), and these compounds alsoserve as a quality index for marine fish.COLORThe first impression that a consumer receives con-cerning a food product is established visually, andamong the properties observed are color, form, andsurface characteristics.Color is the main aspect that defines a food’squality, and a product may be rejected simply be-cause of its color, even before other properties, suchas aroma,texture, and taste, can be evaluated. This iswhy the appearance (optical properties, physicalform, and presentation) of meat and poultry prod-ucts at the point of sale is of such importance for theindustry. Regarding the specific characteristics thatcontribute to the physical appearance of meat andpoultry, color is the quality that most influences con-sumer choice.Food technologists have a special interest in thecolor of food for several reasons. First, because ofthe need to maintain a uniform color throughoutprocessing; second,to prevent any external or inter-nal agent from acting on the product during proces-sing, storage, and display; third, to improve or opti-mize a product’s color and appearance; and, last, toattempt to bring the product’s color into line withwhat the consumer expects.Put simply, the color of meat is determined by thepigments present. These can be classified into thefollowing four types:phenols, and sulfur-containing compounds. The sec-ond is due to water soluble, low molecular weightfree amino acids (taurine,glutamic acid, glycine),nu-Biological (carotenes and haemopigments),which are accumulated or synthesized in theorganism antemortem
1 FactorsAffecting Food Quality 5Pigments produced as a result of damage duringmanipulation or inadequate processingconditionsPigments produced postmortem (throughenzymatic or nonenzymatic reactions)Those resulting from the addition of natural orartificial colorantsAs a quality parameter, color has been widelystudied in fresh-meat and cooked products. Dry-cured meat products have received less attention be-cause in this type of product, color formation takesplace during the different processing stages.Recently, new haempigment has been identified inthis type of product.From a practical point of view, color plays a fun-damental role in the animal production sector, espe-cially in meat production (primarily beef and poul-try,) since in many countries of the European Union,paleness receives a wholesale premium.MICROBIOLOGY AND SAFETYAll foods contain microorganisms, some beneficialto and some with potential harm for mankind. Withmuscle foods, the beneficial ones are responsible forfermented meat and fish. Those potential pathogensare of concern. In the last 25 years, governmentrecords show that pathogenic organisms in meat,poultry, and seafood have been responsible for manydeaths and injuries. Also, marine toxins pose bigthreats to our well-being considering that most of usenjoy eating fish and shellfish. It is not surprisingthat a quality muscle food must also be a safe one.In view of potential hazards from the consump-tion of muscle foods,state and federal agencies havedeveloped and implemented stringent safety re-quirements in the processing of meat, poultry, andseafood.PROCESSINGThe quality of any muscle food is obviously affectedby the way it is processed.Why do we want to process food? At present,there are many modern reasons why foods are pro-cessed, e.g., adding value to a food, improving thevisual appeal, convenience. However, traditionally,the single most important reason that we wish tospoiling. Probably the oldest methods of achievingthis goal are the salting of meat and fish, fermentingof milk, and pickling of vegetables.Foods are made from natural materials, and likeany living matter, will deteriorate in time. The dete-rioration of food, or food spoilage, is the natural wayof recycling, restoring carbon, phosphorus, and ni-trogenous matters to the good earth. However, putre-faction (spoilage) will modify the quality of foodsresulting in poor appearance (discoloration), offen-sive smell, and inferior taste. Food spoilage can becaused by a number of factors, chiefly by biologicalfactors, but also by chemical and physical factors.Consumption of spoiled foods can cause sicknessand even death. There is no doubt none of us con-sider spoiled foods as having quality.Selected examples will illustrate how food pro-cessing can affect the quality of a food product:Heat application. All of us know that over-heating tender meat and chicken usually meanstoughness. The same is especially true forseafood.Heat removal or cold preservation. Freezing is agood example. Most of us are familiar withfreezer-burn of meat, chicken, fish, shellfish, orother products left in the freezer over extendedperiods of time.Evaporation and dehydration. Food drying hasbeen popular since the beginning of time.Destruction of nutrients, especially vitamins, isone drawback to this method of preservation.Fermentation. In general, of meat, poultry, andfish products, fermented meat such as sausages ismost popular. The quality of a sausage is to alarge extent determined by the consumer, e.g.,dry, sweet,salty, and pickled. Each methodaffects the quality in terms of nutrients, hardness,tenderness, and flavor.New technology. There are numerous newtechnologies in food processing such asirradiation, microwaving, and ohmic heating.Each method affects the quality of a food invarious ways.The finished product requires packaging. The ob-vious reason for packaging a food product, musclefoods or other, is to protect the food so it will not beexposed to the elements until it is ready to be pre-Dared and consumed. The aualitv and shelf life of aprocess food is to make them last longer without I I d
6 Part I: General Food Quality Factorsfood, especially a muscle food, depends very muchon the way it is packaged.SENSORY ATTRIBUTESAND THE CONSUMERThe sensory attributes of muscle foods are related tothe senses of taste, smell, sight, feel, and sound. Ofall the foods consumed, muscle foods have the low-est tolerance for complete sensorial acceptability. Amuscle food is either acceptable or unacceptablewith little in between. Predominately, the consumervisually assesses the color and surface texture of themuscle. The preparation technique of consumerchoice is utilized, thereby altering the sensory attrib-utes (usually completely). The consumer cooks orprepares the muscle food as they prefer, changingthe surface color, appearance, and texture. The inter-nal altering of texture and flavor is a result of thepreparation or cooking process as well. This willvary depending on the many methods applied. Forinstance, the muscle may be grilled, baked, broiled,or otherwise prepared, all with different fluctuatingend results. Consumption of muscle foods is one ofthe most pleasurable eating experiences. The satietyvalue applied by the consumption of a muscle foodis great when comparing the satisfying effect offoods in general. This is why the sensorial propertiesof muscle foods can be viewed as often more impor-tant than that of other foods.GOVERNMENT STANDARDSAND SPECIFICATIONSThe technical information in this book is applicableto food scientists and technologists worldwide.However, users from the United States will be veryinterested in the current government standards andspecifications for muscle foods (meat, poultry, andseafood) since such documents usually include qual-ity factors. Since many countries use the UnitedStates as an example in formulating their standardsand specifications for muscle foods, scientists, tech-nologists, and engineers from the international com-munity may also benefit from information includedin the appendix.SUMMARYThis chapter provides a short introduction to the fac-tors affecting the quality of foods, especially musclefoods. More details on most of the factors will beprovided throughout the book.
8 Part I: General Foods Quality FactorsThese regulations cover essential practices to preventfood from being contaminated with biological,chemical and physical hazards, and foreign objects,such as the following:Personnel: Use a hair net.Plants and grounds: Use proper containers andlocations for garbage.Sanitation operations: Keep processed ingredi-ents away from raw ingredients.Sanitary facilities and controls: Maintain restrooms and remove water that collects on thefloor of processing areas.Equipment and utensils: Clean vats daily.Warehouse and distribution: Reduce the pres-ence of rodents; do not transport food ingre-dients in a truck that has not been sanitizedafter transporting pesticides.It is obvious that a careful food processor will be-come familiar with these regulations to make surethat their products are safe for public consumption.With this understanding, this chapter will not pro-vide more details on this topic. Rather, our discus-sion will concentrate on HACCP because one of itsobjectives is to make sure that food processors im-plement CGMPR.HAZARD ANALYSIS CRITICALCONTROL POINTSREGULATIONS OR PROGRAMSIn 1997,the FDA adopted a food safety program thatwas developed nearly 30 years ago for astronauts andis now applying it to seafood, and fruit and vegetablejuices. The agency intends to eventually use it formuch of the U.S. food supply. The program for theastronauts focuses on preventing hazards that couldcause food-borne illnesses by applying science-based controls, from raw material to finished prod-ucts. The FDA’s new system will do the same.Many principles of this new system now called(HACCP) are already in place in the FDA-regulatedLACF industry. Since 1997, the FDA has mandatedHACCP for the processing of seafood, among oth-ers. The FDA has also incorporated HACCP into itsFood Code, a document that gives guidance to andserves as model legislation for state and territorialagencies that license and inspect food service estab-lishments, retail food stores,and food vending oper-ations in the United States.Table 2.1. Current good manufacturing prac-tices regulations as stated in 21 CFR 110(Title 21, United States Code of FederalRegulations, Part 110).21 CFR 110.321 CFR 110.521 CFR 110.1021 CFR 110.1921 CFR 110.2021 CFR 110.3521 CFR 110.3721 CFR 110.4021 CFR 110.8021 CFR 110.93Definitions.Current good manufacturingpractice.Personnel.Exclusions.Plant and grounds.Sanitary operations.Sanitary facilities and controls.Equipment and utensils.Processes and controls.Warehousing and distribution.The USDA has developed HACCP programs formeat, poultry, and other land muscle foods. It is im-portant to realize that the underlying principles arethe same, no matter what the manufacturing process.The same principles apply to the processing of meat,poultry, and seafood. The details vary. The discus-sion in this chapter will concentrate on the princi-ples, citing specific examples for meat, poultry, andseafood.Please note that the word “shall” in a legal docu-ment means mandatoryand is used routinely in USDAFDA regulations published in the U.S. In this chapter,the words “should”and “must”are used to make forsmoother reading. However,this in no way diminishesthe legal impact of the original regulations.WHATIS HACCP?HACCP involves the following seven principles:Analyze hazards. Potential hazards associatedwith a food and measures to control those haz-ards are identified. The hazard could be biolog-ical, such as a microbe; chemical, such as atoxin; or physical, such as ground glass ormetal fragments.Identify critical control points. These are pointsin a food’s production-from its raw statethrough processing and shipping to consump-tion by the consumer-at which the potentialhazard can be controlled or eliminated.Examples are cooking, cooling, packaging, andmetal detection.
2 HACCP and Muscle Food Safety in the United States 220.127.116.11.7.Establish preventive measures with critical lim-its for each control point. For a cooked food,for example, this might include setting the min-imum cooking temperature and time requiredto ensure the elimination of any harmful mi-crobes.Establish procedures to monitor the criticalcontrol points. Such procedures might includedetermining how and by whom cooking timeand temperature should be monitored.Establish corrective actions to be taken whenmonitoring shows that a critical limit has notbeen met-for example, reprocessing or dis-posing of food if the minimum cooking tem-perature is not met.Establish procedures to verify that the systemis working properly-for example, testing timeand temperature recording devices to verifythat a cooking unit is working properly.Establish effective record keeping to documentthe HACCP system. This would includerecords of hazards and their control methods,the monitoring of safety requirements and ac-tion taken to correct potential problems.Each of these principles must be backed by soundscientific knowledge such as published microbiolog-ical studies on time and temperature factors for con-trolling food-borne pathogens.THENEEDFOR HACCPNew challenges to the U.S. food supply haveprompted the USDA and FDA to consider adoptingan HACCP-based food safety system on a wider ba-sis. One of the most important challenges is the in-creasing number of new food pathogens. There alsois increasing public health concern about chemicalcontamination of food, for example, the effects oflead in food on the nervous system.Another important factor is that the size of thefood industry and the diversity of products and pro-cesses have grown tremendously, in the amount ofdomestic food manufactured and the number andkinds of foods imported. At the same time, federal,state, and local agencies have the same limited levelof resources to ensure food safety. The need forHACCP in the United States, particularly in theMUSCLE food industries, is further fueled by thegrowing trend in international trade for worldwideequivalence of food products and the CodexAlimentarius Commission’s adoption of HACCP asthe international standard for food safety.ADVANTAGESAND PLANSHACCP offers a number of advantages over previ-ous systems. Most importantly, HACCP:18.104.22.168.5.6.focuses on identifying and preventing hazardsfrom contaminating food.is based on sound science.permits more efficient and effective govern-ment oversight, primarily because the recordkeeping allows investigators to see how well afirm is complying with food safety laws over aperiod rather than how well it is doing on anygiven day.places responsibility for ensuring food safetyappropriately on the food manufacturer or dis-tributor.helps food companies compete more effec-tively in the world market.reduces barriers to international trade.The seven steps used in HACCP plan develop-ment follow:1. Preliminary Stepsa. General informationb. Describe the foodc. Describe the method of distribution andstoraged. Identify the intended use and consumere. Develop a flow diagram2. Hazard Analysis Worksheeta.b.C.d.e.f.g.Set up the Hazard Analysis WorksheetIdentify the potential species-relatedhazardsIdentify the potential process-relatedhazardsComplete the Hazard Analysis WorksheetUnderstand the potential hazardDetermine if the potential hazard is significantIdentify the critical control points (CCP)3. HACCP Plan Forma. Complete the HACCP Plan Formb. Set the critical limits (CL)
10 Part I: General Foods Quality Factors4. Establish Monitoring Proceduresa. Whatb. Howc. Frequencyd. Who5. Establish Corrective Action Procedures6. Establish a Record Keeping System7. Establish Verification ProceduresIt is important to remember that apart from HAC-CPR promulgated for seafood and juices, the imple-mentation of HACCP by other categories of foodprocessing is voluntary. However, the FDA and var-ious types of food processors are working togetherso that eventually HACCPR will become availablefor many other food processing systems under FDAjurisdiction. Using the HACCPR for seafood pro-cessing as a guide, the following discussion for anHACCP plan applies to all categories of food prod-ucts being processed in the United States.HAZARDANALYSISEvery processor should conduct a hazard analysis todetermine whether there are food safety hazards thatare reasonably likely to occur for each kind of prod-uct processed by that processor and to identify thepreventive measures that the processor can apply tocontrol those hazards. Such food safety hazards canbe introduced both within and outside the proces-sing plant environment, including food safety haz-ards that can occur before, during, and after harvest.A food safety hazard that is reasonably likely to oc-cur is one for which a prudent processor would es-tablish controls because experience, illness data, sci-entific reports, or other information provide a basisto conclude that there is a reasonable possibility thatit will occur in the particular type of product beingprocessed in the absence of those controls.THEHACCP PLANEvery processor should have and implement a writ-ten HACCP plan whenever a hazard analysis revealsone or more food safety hazards that are reasonablylikely to occur. An HACCP plan should be specificto the following:1.2.Each location where products are processed bythat processor.Each kind of product processed by the processor.The plan may group kinds of products together, orgroup kinds of production methods together, if thefood safety hazards, CCPs, CLs,and procedures thatare required to be identified and performed are iden-tical for all products so grouped or for all productionmethods so grouped.The Contents of the HACCP PlanThe HACCP plan should, at a minimum:List the food safety hazards that are reasonablylikely to occur, as identified, and that thus must becontrolled for each product. Consideration shouldbe given to whether any food safety hazards arereasonably likely to occur as a result of the follow-ing: natural toxins; microbiological contamination;chemical contamination; pesticides; drug residues;decompositionin productswhere a food safety haz-ard has been associated with decomposition; para-sites, where the processor has knowledge that theparasite-containingproduct will be consumedwith-out a process sufficient to kill the parasites; unap-proved use of direct or indirect food or color addi-tives; and physical hazards;List the critical control points for each of theidentified food safety hazards, including as appro-priate: critical control points designed to controlfood safety hazards that could be introduced in theprocessing plant environment; and critical controlpoints designed to control food safety hazards in-troduced outside the processing plant environment,including food safety hazards that occur before,during, and after harvest;List the critical limits that must be met at eachof the critical control points;List the procedures, and frequency thereof, thatwill be used to monitor each of the critical controlpoints to ensure compliance with the critical limits;Include any corrective action plans that havebeen developed to be followed in response to devi-ations from critical limits at critical control points;List the verification procedures, and frequencythereof, that the processor will use;Provide for a record keeping system that docu-ments the monitoring of the critical control points.The records should contain the actual values andobservationsobtained during monitoring.Signingand Dating the HACCP PlanThe HACCP plan should be signed and dated eitherby the most responsible individual on site at the pro-cessing facility or by a higher-level official of the
2 HACCP and Muscle Food Safety in the United States 11processor. This signature should signify that theHACCP plan has been accepted for implementationby the firm.It should be signed and dated upon initial accep-tance; upon any modification; and upon verificationof the plan.SANITATIONSanitation controls (3) may be included in theHACCP plan. However, to the extent that they areotherwise monitored, they need not be included inthe HACCP plan.IMPLEMENTATIONThis book is not the proper forumto discuss in detailthe implementation of HACCPR. Readers interestedin additional information on HACCP should visitthe FDA HACCP website http://vm.cfsan.fda.gov/that lists all of the currently available documents onthe subject.REFERENCESFood and Drug Administration. 2006. Current GoodManufacturing Practice in Manufacturing, Packing,or Holding Human Food. 21 CFR 110. U.S.Government Printing Office, Washington, DC.Food and Drug Administration. 2006. Hazard Analysisand Critical Control Point (HACCP) Systems. 21CFR 120. U.S. Government Printing Office,Washington, DC.Food Safety and Inspection Service, USDA. 2006.Hazard Analysis and Critical Control Point(HACCP) Systems. 9 CFR 417. U.S. GovernmentPrinting Office, Washington, DC.
16 Part 11:Sensory Attributes of Muscle Foodsmechanical properties of foods,detected through thesenses of vision, hearing, touch, and kinesthetics(Szczesniak 1963) and consists of hardness, cohe-siveness, adhesiveness, denseness, springiness, per-ception of particles, and perception of water. Theseattributes are perceived by sensors in the mouth bothbefore and after chewing and have been describedextensively (Brandt and others 1963; Szczesniak1963;Szczesniak and others 1975). Flavor includesaromatics, tastes, and chemical feelings. Aromaticsconsist of olfactometry perceptions caused byvolatile substances released from a product in themouth. Tastes consist of salty, sweet,sour, and bitterperceptions caused by soluble substances in themouth, and chemical feelings include astringency,spice heat, cooling, and metallic flavor. Flavor iscrucial in the acceptance of food, and the use offlavor-related words is a very important aspect ofmarketing (Amerine and others 1965).The NationalResearch Council (1988) reported that the threemost important factors that consumers look for inmeat products are nutrition, price, and taste. How-ever, if taste is not acceptable, then nutrition andprice are irrelevant.Stone and others (1991) have reported that thou-sands of new products are unsuccessfully introducedto the retail market every year. With the continuedinflux of new products into the market, sensory eval-uation has become increasingly important to foodcompanies in the creation of new food products aswell as in determining the quality attributes of prod-ucts within a competition category. Marketing andsensory evaluation departments must work togetherto bring the appropriate new product to market. Bothgroups have equally important roles that must be un-derstood by each other as well as by upper manage-ment to perform the appropriate market research,trained panel sensory evaluations, and consumertesting. This book will provide an in-depth look atthe sensory characteristics of all muscle foods fromboth a trained panel and a consumer panel perspec-tive through discussing the important sensory attrib-utes as well as the sensory methods utilized to eval-uate beef, pork, poultry, seafood, processed musclefoods, as well as lamb, venison, bison, and equine.HISTORY OF MUSCLE FOODSMuscle foods or meats can be defined as flesh fromanimals that is suitable for consumption (Kinsmanand others 1994), and first became a steady foodsource in the diet between 10,000and 16,000yearsago as animals were domesticated and people be-came less nomadic in nature (Kinsman 1994).Refer-ences have been made in the Iliad and in theOld Testament to meat consumption that has beencarbon dated back greater than 3,000 years, and themeat industry in the United States evolved fromColumbus and Cortez bringing cattle, hogs, andsheep to North America in 1493 and 1519, respec-tively. The history of the meat industry will not bediscussed in this chapter, but an informative per-spective on the history of this exciting industry canbe found in Kinsman (1994). The seafood industryalso has an exciting history in which large humanpopulations tended to settle near seas or large riversystems where fish and shellfish were readily abun-dant as food. References to fishing have also beenmade in the Old and New Testament of the Biblecarbon dating back thousands of years. As time pro-gressed, larger fish were desired and fishermen builtboats to travel further from shore. Quite often fishingwas the reason for discovering new lands, and the ex-cellent fishing possibilities in the North AtlanticOcean lured fishermen to North America fromEurope leading to commercial fishing becoming thefirst industry in the New World (Martin 1990). Thehistory of this diverse industry will not be discussedin detail, but there is an excellent account of this his-tory in Martin (1990).U.S. meat and poultry products consumption hasfluctuated between 87 and 100 kilograms (kg) percapita consumption between 1980 and 2001, respec-tively (American Meat Institute [AMI] 2003), andseafood products consumption has held steady at 5to 7 kg per capita between 1960 and 2002 (AM11993; NMFS 2002). This demonstrates the stayingpower of meat products in the food industry. Mealswill continue to be planned around meat productsfor two reasons. First, muscle foods are the mostnaturally occurring nutrient-dense foodstuff (Kins-man 1994). Second, meat products are of vital im-portance in providing high quality proteins, miner-als, vitamins, and a high satiety value (Price andSchweigert 1987).With the high percentage of two-parent wage earners, there will be a greater need anddemand for more table-ready and microwaveablefoods that require minimum preparation time(Kinsman 1994).This will lead to an increased im-portance of sensory testing since all meat products
3 History, Background, and Objectives of SensoIy Evaluation in Muscle Foods 17of these types must be evaluated for sensory quality(appearance, odor, texture, and flavor).HISTORY, BACKGROUND, ANDDEVELOPMENT OF SENSORYEVALUATIONMuch literature has been reported pertaining to theevolution of sensory evaluation into the complexscience that it is currently. Likewise, the practice ofusing a trained panel to relate product attributes toconsumer acceptability in the successful develop-ment of food products is well documented. The prin-cipal sources behind the science of sensory evalua-tion as it is studied today are psychology, physiology,sociology, and statistics (Peryam 1990). The psy-chophysical roots for sensory evaluation can betraced to the work of Weber, a German physiologist(Boring 1950), but it was Fechner, a German psy-chologist, who built on the observations of Weber inorder to demonstrate a link between the physical andpsychological worlds. Weber found that differencethresholds, the extent of changes in stimuli neces-sary to produce noticeable differences, increase inproportion to the initial perceived stimulus intensityat which they are measured. Fechner then utilizedthe findings of Weber to demonstrate that perceivedmagnitude may be related to the change in intensityand absolute intensity of a sensation. The combinedefforts of these two scientists laid much of thegroundwork during the late nineteenth century forthe field of psychometrics that deals with the mathe-matical explanation of psychological phenomena.The development of statistical methods (duringthe nineteenth century) that are currently utilized insensory evaluation was also essential in the founda-tion of this discipline. When sensory evaluationstarted to show life in the 1930s, many statisticalprocedures including analysis of variance were al-ready in place to describe the variation in perceptionand behavior of people evaluating food products(Peryam 1990). The evolution of sensory science asit is practiced today originated in the 1930s aroundthe time of the organization of the Institute of FoodTechnologists. During this time, sensory informa-tion was largely confined to recording opinions ofone or two experts evaluating the quality of a spe-cific commodity in order to provide quality controlfor their organization’s products (Pangborn 1964).The problem with this type of sensory evaluationwas that it did not necessarily reflect consumer atti-tudes. In a regional environment, utilizing one ortwo experts was extremely helpful in determiningproduct quality, but Hinreiner (1956) stated that cer-tain values on scorecards can become fixed in theexpert’s minds as acceptable to consumers that donot necessarily reflect consumer attitudes. Stone andSide1 (1993) stated that though this approach iscommon in quality control, its prevalence in sensoryevaluation reflects a basic lack of understanding ofhuman behavior or the wistful desire of some to re-duce response behavior to some simplistic level.Platt (1931) recommended that critical experts beeliminated, and thatjudges be selected for participa-tion on sensory panels on the basis of being able topredict public preference. Platt understood the im-portance of meeting the needs and wants of the con-sumer, but the consumer testing and trained paneltesting necessary to accomplish this goal was not yetavailable to the industry.Dove (1947) reported that food acceptance re-search was a result of rationing of foods to thetroops in World War 11.Rations were tested for qual-ity specifications on a nutritional basis. However,the soldier-consumer refused to eat some rations,which ended up in storage dumps. This occurrenceled to an official directive to determine causes of un-acceptance. These food products had been tested fornutrition, tenderness, viscosity, compression, flavor,and quality, or had been tested by scorecard ratings.These methods had all been applied, and the foodwas still rejected. In this objective approach, mea-surements are directed toward the food. However,the subjective test deals with an individual’sphysio-logical or psychological response. These occurrencesled to an impetus in sensory evaluation developmentthrough the U.S. Army Quartermaster Food andContainer Institute, an organization that supportedresearch in the acceptance of food products con-sumed by the armed forces (Peryam 1990). Duringthis time period, the U.S. Army Quarter-masterFood and Container Institute made many great con-tributions to sensory evaluation research. The mostwell-known contribution was the “invention” of the9-point hedonic scale (Peryam and Pilgrim 1957).Another outstanding contribution of the Institutewas undoubtedly the collaboration between psy-chologists, food technologists, and statisticians.This multidisciplinary collaboration is a good modelfor the scientists that should be working together to
18 Part 11:Sensory Attributes of Muscle Foodsperform sensory evaluation on all foods, includingmuscle foods. The importance of sensory accep-tance was then quickly forgotten by the federal gov-ernment as they initiated their “War on Hunger”and“Food from the Sea” programs (Stone and Side11993) in which the government’s intention was tofeed starving and malnourished people even thoughno research was performed on whether the productsbeing provided were acceptable to the targetedgroups.During a similar time period, many developmentswere occurring in the private sector relating to theuse of both affective testing as well as trained pan-elists to explain the quality of food products. In thelate 1940s, the Kroger company started performingaffective consumer tests by sending samples tohousewives (Peryam 1990). This innovative ideawas very informal but provided an impetus towardconsumer tests that are utilized today. The duo-triotests and triangle tests were also developed duringthe 1930s and 1940s by Seagram Distillers and re-searchers in Europe (Peryam 1990) in order to main-tain uniform quality in standard products. This wasthe beginning of the development of trained panelmethods that are currently used. In the 1950s, theflavor profile analysis was first developed by ArthurD. Little in Cambridge, Massachusetts, to provideinformation about the complexities of perception offlavor characteristics and their relation to the physi-cal components of food products (Cairncross andSjostrom 1950). This methodology led others to in-troduce texture profile analysis (Brandt and others1963;Szczesniak 1963) and quantitative descriptiveanalysis (Stone and others 1974),respectively. Crossand others (1978) adapted this methodology into adescriptive analysis method that is now commonlyutilized in muscle foods (AMSA 1995).During this time period, former departments ofdairy science, meat science,and other food productsmerged into departments of food science and tech-nology, and researchers began to relate sensory eval-uation or subjective testing to objective tests such asthe Instron and gas chromatograph (GC) (Pangborn1989). Academic endeavors in evaluating sensoryproperties of foods date back to the mid-1930s.TheUniversity of California at Davis has contributedgreatly to the scientific community from an academicviewpoint. Maynard Amerine and his associateswere followed by Rose Marie Pangborn and hercoworkers utilizing the best techniques availableand developing new techniques and effective varia-tions of tests (Peryam 1990). Currently, sensoryevaluation is taught in connection with many foodscience and nutrition curricula, and many universi-ties now offer a Ph.D. in sensory science with an ar-ray of multidisciplinary courses. Pangborn (1989)stated that the industrial demand for well-trainedsensory professionals at the B.S., M.S., and Ph.D.levels greatly exceeds the supply, a statement that isstill true today. Another development that has madea huge impact on sensory science in recent years(1969-1988) is the development of journals such asJournal of Texture Studies, Chemical Senses,Journal of Food Quality, Appetite, Journal ofSensory Studies, and Food Quality Preference(Pangborn 1989). These journals have improved thelevel of applied sensory science by providing bothincreased avenues for scientists to share their find-ings and method developments with the scientificcommunity. Sensory evaluation has now evolvedinto testing that can use complicated multivariateanalysis as well as mathematical modeling and otherstatistical analyses to evaluate data. This has al-lowed for excellent connections between trainedsensory panels and consumer data. However, nomatter how complicated the analysis, it is crucialthat the sensory design be set up appropriately, orthe data will be meaningless. This is of increasedimportance when dealing with human subjects.Human panelists are more sensitive than instrumentsbut are also more variable.OBJECTIVESThe objectives of sensory evaluation can be dividedinto two categories. The first can be viewed as thepurpose of sensory evaluation. This purpose is to de-termine product quality and ultimately provide theconsumer with the products that they desire. Thesecond category can be viewed as the actual objec-tives that must be followed in conducting sensorytesting that are both specific and nonspecific to mus-cle foods.DETERMININGQUALITYAND CONSUMERACCEPTABILITYThe objective of providing the consumer with de-sired products requires two kinds of information-sensory descriptive and preference (quality) judg-
3 History, Background, and Objectives of SensoIy Evaluation in Muscle Foods 19ments. The former are usually obtained from atrained panel and the latter are obtained from appro-priately recruited and qualified consumers (Stoneand others 1993). These two goals can be brokendown further into four types of tests, each with theirown objective. These tests include affective, dis-criminative, descriptive, and quality tests (Sidel andothers 1981).Affective tests are generally utilized toindicate preference or acceptance of productsthrough selecting, ranking, or scoring samples bypanelists that represent the target consumer popula-tion. Discrimination tests are utilized to test whethersamples are different from one another and shouldusually be run with trained panels. Some discrimina-tion tests such as triangle tests can also be utilized inpanel selection for descriptive tests. Descriptivetests describe sensory properties and measure theperceived intensity of those properties. The twomost popular descriptive methods include classicaland modified flavor profile (Cairncross and Sjostrom1950),texture profile (Brandt and others 1963),andquantitative descriptive analysis (Stone and others1974). Cross and others (1978) later adapted thesemethods in the creation of a descriptive attributepanel intended for the evaluation of meat products.The Spectrum method published by Meilgaard andothers (1991)further enhances descriptive testing byadapting the test to the product being evaluatedthrough the use of reference points. These are indi-cated by intensities of descriptors in specific com-mercially available foods. This scale prevents pan-elists from avoiding the ends of the scale,which is amajor problem with fixed scales. The fourth type oftesting utilized is quality testing in which one or twoexperts are utilized to test a product to determine if itmeets quality specifications. This method can workwell when it is solely used to see if a product meetsspecifications, but it should not be assumed thatthese judgments by trained experts directly relate toconsumer preference or acceptance of food prod-ucts. Typically, physical and chemical instrumentalmeasurements should also be incorporated in testingto relate instrumental measurements of quality tosensory perceptions of quality. Therefore, it can bestated that the ultimate objective of sensory evalua-tion is to predict consumer acceptability, but thiscannot be done without trained sensory panels andinstrumental measures to relate to preference test-ing. This objective can be accomplished through dif-ferent means, but the company that has this capabil-ity and is able to exploit this knowledge hasachieved a major accomplishment (Stone and Sidel1993).PRACTICALOBJECTIVESOF SENSORYEVALUATIONIn dealing with a subject’ssensory responses, thereis a three-step mechanism (Meilgaard and others1991).First, a sensation results from a stimulus thatis detected by a sense organ and travels to the brainas a nerve signal. The brain is then utilized to trans-pose the sensations into perceptions, and lastly, aresponse is formulated based on the subject’s per-ceptions (Carlson 1998).This causes much greatervariability when utilizing humans as instrumentssince this three-step process exists in comparison toa one-step process that exists in other instrumentaltests. The complexity of sensory evaluation makesit imperative that a specific process be taken inthe design of sensory evaluation experiments.Pangborn (1979) states that there are three commonproblems to sensory evaluation that include lack oftest objective, adherence to a single test method re-gardless of application, and improper subject selec-tion procedures. These three details must be ad-dressed in all sensory analyses. Erhardt (1978)reports that there is a specific role of the sensory an-alyst that can be broken down into seven tasks. Thefollowing is a paraphrased version of these sevensteps that are discussed in detail in that paper. Thefirst step in conducting a sensory experiment is todetermine the project objective. The next step is todetermine the test objective to assure that the result-ing data will be relevant to the overall objective ofthe sensory project. The third step for the analyst isto screen samples. This allows the analyst to be-come familiar with the responses that might be ex-pected, minimizes the evaluation of obviously dif-ferent samples, and helps the analyst to design thetest. The next step for the sensory analyst is to de-sign the test. The correct time to consider experi-mental design and statistical analyses is after a testis planned and not at the conclusion of the work.The next step is to conduct the test. When conduct-ing a test, it is imperative that the procedures arestrictly adhered to in order to prevent nontest vari-ables from influencing panelist responses and/orperception. The last two responsibilities of the sen-sory analyst are to analyze data according to the
20 Part 11:Sensory Attributes of Muscle Foodspredetermined statistical analyses and to report theresults to the entity that requested the research. Theanalyst must make it clear to the requester what testresults mean, the conclusion that can be drawn fromthe results, and the next step to take based on theinitial project objective.SENSORY EVALUATION SPECIFICTO MUSCLE FOODSSensory evaluation as it is currently practiced formuscle foods is documented by the American MeatScience Association (AMSA 1995).Through the useof sophisticated panel training and method selec-tion, sensory evaluation can provide accurate and re-peatable data. Sensory factors in meat include ten-derness, juiciness, flavor and aroma, and color(Cross 1987). Cross and others (1978) originated themost commonly utilized method for descriptiveanalysis in the testing of meat products. This is themost referenced method for descriptive testing inmuscle foods, thus implying that it is also the mostutilized method. Consumer testing of meat productsis generally performed with affective tests of accep-tance or preference that are utilized for all foodproducts. Those tests that were termed consumerguidance tests in Griffin (1999) should be utilizedalong with market research tests in the developmentof food products in the industry. There is a clear dis-tinction between the two types of testing, and it isthe sensory scientist’s responsibility to help uppermanagement understand this in order to provideproducts to the consumer that will be successful forthe company (Griffin 1999).TRAINEDPANELSTrained panels are utilized to provide accurate andrepeatable data pertaining to the quality of meatproducts. Cross and others (1978) reported foursteps that should be taken in the selection of atrained panel including recruitment, screening,training, and performance evaluation. A sensorystudy should only be initiated after all of these stepshave been taken (AMSA 1995; Cross and others1978).Trained tests in muscle foods include rankingand scaling of samples, magnitude estimation, anddescriptive sensory analysis. The second of thesemethods has limitless applications. It has been uti-lized to relate to physical and chemical analyses,product formulations, preferences, and other kindsof consumer measures of concepts, pricing, and soforth (Stone and Side1 1998). Descriptive analysesare very important to the meat industry since theyare useful in investigating treatment differences,monitoring ingredient process control criteria, anddefining sensory properties of a target product (Bett1993).CONSUMERPANELSKauffman (1993) stated that meat quality includesseven variables: wholesomeness, nutrition, proces-sing yield, convenience, consistency, appearance,and palatability. Palatability has five components:tenderness, texture, juiciness, and flavor (odor andtaste) (Kauffman and others 1990). Booth (1990)stated that people eat foods they like, includingmeat, and sensory properties impact those likes.However, Logue and Smith (1986) reported that lik-ing fresh meat was not related to liking fish, and nei-ther of those was related to liking restructured meatproducts. This demonstrates that consumers expectand emphasize different sensory characteristics forvarious meat products (Chambers and Bowers1993). For example, consumer studies have revealedthat tenderness is the most important attribute ofbeef (AMSA 1978) and chicken, but this attribute isnot as important in other species since it is not asvariable. This has led to researchers determining therelationship between consumer acceptability andobjective measurements of tenderness in meat prod-ucts (Lyon and others 1990; Schilling and others2003). These factors are measured objectively, butthe most important perception is evaluated by sen-sory panels. Since meat cookery has a significant in-fluence on sensory characteristics, its selection is anintegral part of sensory evaluation (Cross 1987).Thesensory properties that consumers want depend onspecies as well as whether the food is being pur-chased, stored, cooked, or eaten (Chambers andBowers 1993). To fully understand consumer ac-ceptability testing in meat products, it must be un-derstood what attributes are important to consumersfor each particular study. Objectives will often besimilar when testing different muscle food products,but quality attributes that are important to con-sumers may differ among different muscle foodproducts.
3 History, Background, and Objectives of SensoIy Evaluation in Muscle Foods 21RELATIONSHIPOF CONSUMERPANELSTO TRAINED PANELSElrod (1978) reported that many companies arestructured so that trained panels are utilized to de-sign products and then the marketing department isresponsible for consumer testing if it is performed.To produce the best possible product, it is imperativefor marketing and research and development depart-ments to relate all market research, consumer test-ing, and trained sensory evaluation. Munoz andChambers (1993) describe a model for relating de-scriptive analysis techniques and objective testing toconsumer acceptability. These authors report thatthis approach can provide the following usefulpieces of information. First, actionable productguidance will be provided that is based on attributesfor product formulation and reformulation toachieve high consumer acceptance. Second, the at-tributes that affect consumer acceptability can be de-termined. Third, laboratory data can be used to pre-dict consumer response and determine its usefulnessin explaining consumer responses. Fourth, appropri-ate marketing terms can be identified that coincidewith consumers desires, and lastly, it allows re-searchers to interpret and understand consumer ter-minology.QUALITY CHARACTERISTICSIn general, it has been reported that tenderness, acomponent of texture, is the most important at-tribute of fresh meat products, and has thus beenstudied more with consumers than other properties.This may be in part due to the broad range in ten-derness of products not seen in other quality charac-teristics. Cross and Stanfield (1976) and Diamantand others (1976) have reported that tenderness wasthe most important attribute in determining accept-ability in restructured beef steaks and cooked porkchops, respectively. If a product is not tender, it isautomatically deemed unacceptable. Textural char-acteristics of muscle food products are often evalu-ated using trained texture profile analyses. Thismethodology is most often utilized in processedmeat products and the characteristics studied aregenerally hardness, springiness, chewiness, gummi-ness, and cohesiveness.Color is one of the most important characteristicsof meat since it is the primary attribute by whichboth fresh and cured meats are judged by the con-sumer before purchase (Fox 1987). Two commonexamples of this are the preference of purchasingbeef that is cherry red in color and the lack of con-sumer acceptability for pork and poultry productsthat are pale in color (Kropf 1980).Flavor is a very important sensory attribute inmuscle foods, but this attribute cannot be explainedwell by consumers since their vocabulary is insuffi-cient to describe the complex flavors found in mostmeat products (Chambers and Bowers 1993). Forthis reason, flavor intensity and off-flavor are usu-ally the only flavor characteristics determined inconsumer studies. However, these variables may notbe well understood by consumers. Chambers andothers (1992) concluded that off-flavor as describedby consumers was characterized as soapy by a de-scriptive panel. This reveals that the consumers werenot really distinguishing off-flavors at all. They werereally distinguishing the soapy flavor that can be afunction of phosphate addition in processed meatproducts. In trained panels, descriptive analysis pro-cedures have been utilized to accurately characterizemeat flavor from different species as well as pro-cessed meat products. Volatiles extracted from meatproducts that are responsible for these flavors havebeen characterized utilizing gas chromatography(GC), GC-mass spectrometry (GC-MS), and GC-olfactometry (GC-0).Sensory evaluation is commonly utilized in deter-mining the shelf life of muscle food products. Bothanalytical and affective testing can be effective indetermining shelf life, and the simultaneous use ofboth tests allows the best determination of how longthe product will have acceptable quality (Dethmers1979). This testing will allow for determinations ofexpiration, freshness or quality assurance, and packdates. A product’s shelf-life is determined by bacter-ial or enzymatic spoilage, loss of aesthetic qualities,physical changes such as moisture evaporation,chemical reactions such as oxidation, contaminationfrom storage environment, loss of nutritive value,and interactions between product and package con-ditions (IFT 1974). Sensory evaluation will allowfor determination of manufacturing, packaging, andstoring conditions that will minimize these deterio-rations from occurring. Such shelf life determina-tions follow a similar pattern to the relationships be-tween consumer and trained sensory panels asdescribed by Murioz and Chambers (1993).
22 Part 11:Sensory Attributes of Muscle FoodsNOVELUSESOF STATISTICALMETHODSFour novel methods that have come to fruition overthe last 10 to 15 years include response surfacemethodology, principal components analysis, princi-pal factor analysis, and logistic regression. The po-tential for the relation of trained sensory panels toobjective measurements and consumer acceptabilityis very exciting. Also, the possibility for buildingflavor languages for food products based on brand,region, or other appropriate attributes will allow forthe determination of consumers’ desires in regionsas well as allow for increased communicationamong researchers working in different parts of thecountry. Novel approaches to statistical design ofsensory experiments and analysis of sensory dataare being developed or adapted to this discipline allof the time. These novel statistical methods are valu-able tools, but they should never take the place ofcommon sense and clearly understanding the objec-tive of the study. Utilizing computers has also in-creased the number of possibilities available for an-alyzing sensory data. This is excellent in that itmakes it much easier to run complicated regressionand multivariate analyses. However, utilizing com-puter programs can also be dangerous since theywill give you incorrect results if you do not under-stand the experimental design and/or the computerprogram. Substitution of statistical programs forpractical knowledge of sensory evaluation and dataanalysis is a danger that must be avoided. The possi-bilities and applications of logistic regression andvarious multivariate analyses are limitless in theirapplication as far as relating trained data to con-sumer data, in determining shelf life, and in productdevelopment. Proper use of these experimental de-signs and statistical packages will help contribute toa company providing products that are desired byconsumers.CONCLUSION AND FUTURE OFSENSORY EVALUATIONAs food technology becomes more complex, the ba-sics of sensory evaluation need to be remembered.The goal of sensory evaluation is to explain the con-sumer acceptability of food products. This can onlybe done through utilization of the four sensorymethodologies listed in this chapter and working to-gether with the market research department to makesure that the appropriate questions and problems arebeing answered and solved. Education on appropri-ate utilization of sensory analysis must be contin-ued. It is clear that most companies are utilizing sen-sory analysis, but quite often, the wrong methods arebeing utilized for the stated objectives of the studies(Stone and Side1 1993).This book will provide a ba-sic understanding of sensory properties and evalua-tion as they relate to muscle foods.REFERENCESAmerican Meat Institute. 1993. Meat Facts. AmericanMeat Institute, Washington, DC.American Meat Institute. 2003. Overview of U.S. Meatand Poultry Production and Consumption. AM1 FactSheet. www.meatami.com.Amerine, MA, RM Pangborn, and EB Roessler. 1965.Principles of sensory evaluation of food. New York:Academic Press, p. 602.AMSA. 1978. Guidelines for Cookery and SensoryEvaluation of Meat. Am. Meat Sci. Assoc. and Natl.Live Stock and Meat Board, Chicago, Ill.AMSA. 1995. Research Guidelines for Cookery,Sensory Evaluation and Instrumental TendernessMeasurements of Fresh Meat. Am. Meat Sci. Assoc.and Natl. Live Stock and Meat Board. Chicago, Ill.Anonymous. 1975. Minutes of Division BusinessMeeting. Institute of Food Technologists, SensoryEvaluation Division, IFT, Chicago, Illinois.Bett, KL. 1993. Measuring sensory properties of meatin the laboratory. Food Technol, 47(11), pp. 121-2,124-6.Booth, DA. 1990. Sensory influences on food intake.Nut Rev, 48(2),pp. 71-7.Boring, EG. 1950. A History of ExperimentalPsychology. 2nd ed. Appleton, New York.Brandt, MA, E Skinner, and J Coleman. 1963. Textureprofile method. J Food Sci, 28, pp. 404-10.Cairncross, WE, and LB Sjostrom. 1950. Flavor pro-file-a new approach to flavor problems. FoodTechnol, 4, pp. 308-1 1.Carlson, NR. 1998. Physiology of Behavior. 6th ed.,Boston, Massachusetts: Allyn and Bacon Inc., p.736.Chambers, E, and JR Bowers. 1993. Consumer percep-tion of sensory qualities in muscle foods. FoodTechnol, 47(11), pp. 116-20.Chambers, L, E Chambers, IV, and JR Bowers. 1992.Consumer acceptability of cooked stored groundturkey patties with differing levels of phosphate. JFood Sci, 57, pp. 1026-8.
3 History, Background, and Objectives of SensoIy Evaluation in Muscle Foods 23Cross, HR. 1987. Sensory Characteristics of Meat. Part1 ~ Sensory Factors and Evaluation. In: Price, JF, BSSchweigert, editors. The Science of Meat and MeatProducts. 3rd ed. Westport, Connecticut: Food andNutrition Press, Inc. pp. 307-27.Cross, HR, R Moen, and MS Stanfield. 1978. Trainingand testing of judges for sensory analysis of meatquality. Food Technol., 32, pp. 48-52, 54.Cross, HR, and MS Stanfield. 1976. Consumer evalua-tion of restructured beef steaks. J Food Sci, 41, pp.1257-8.Dethmers, AE. 1979. Utilizing sensory evaluation todetermine product shelf life. Food Technol, 33(9),pp. 40-2.Diamant, R, BM Watts, and RL Cliplef. 1976.Consumer criteria for pork related to sensory, physi-cal, and descriptive attributes. Can Inst Food Sci andTechnol J, 9(3),pp. 151-4.Dove, WF. 1947. Food acceptability; Its determinationand evaluation. Food Technol, 1, pp. 39-50.Elrod, J. 1978. Bridging the gap between laboratoryand consumer tests. Food Technol, 32(1l),p. 63.Erhardt, JP. 1978. The role of the sensory analyst inproduct development. Food Technol, 32(1l),pp. 57-60.Fox, JB. 1987.The Pigments of Meat. In: Price,JF, andBS Schweigert, editors. The Science of Meat andMeat Products. 3rd ed. Westport, Connecticut: Foodand Nutrition Press, Inc., pp. 193-216.Griffin, RW. 1999. Applied sensory science and con-sumer testing in the industry: history and future.Food Testing and Analysis, 5(2), pp. 9-13, 28.Hinreiner, EH. 1956. Organoleptic evaluation by indus-try panels-the cutting bee. Food Technol, 10, pp.62-7.IFT. 1974. Shelf life of foods. Institute of FoodTechnologists expert panel on food safety and nutri-tion. J Food Sci, 39, p. 861.Kauffman, RG. 1993.Opportunities for the meat indus-try in consumer satisfaction. Food Technol, 47(11),pp. 132-4.Kauffman, RG, W Sybesma, and G Eikelenboom.1990. In search of quality. J Inst Can Sci TechnolAliment, 23, pp. 160-164.Kinsman, DM. 1994. Historical Perspective andCurrent Status. In: Kinsman, DM, AW Kotula, andBC Breidenstein, editors. Muscle Foods. New York:Chapman & Hall, pp. 1-24.Kinsman, DM,AW Kotula, and BC Breidenstein. 1994.Muscle Foods. New York: Chapman & Hall, p. 573.Kropf, DH. 1980. Effects of retail display conditionson meat color. In: American Meat ScienceAssociation. Proc. 33rd Reciprocal Meat Confer-ence. June 20-25,West Lafayette, Indiana, pp. 15-32.Logue, AW, and ME Smith. 1986. Predictors of foodpreferences in adult humans. Appetite, 7, pp. 109-25.Lyon, CE, and BG Lyon. 1990.The relationship of ob-jective shear values and sensory tests to changes intenderness of broiler breast meat. Poultry Sci, 69, pp.329-40.Martin, RE. 1990. A history of the seafood industry. In:Martin, RE, and GJ Flick, editors. The SeafoodIndustry. NewYork:Van Nostrand Reinhold, pp. 1-16.Meilgaard, M, GV Civile, and Carr BT. 1991. SensoryEvaluation Techniques. 2nd ed., Boca Raton,Florida: CRC Press, p. 354.Munoz, AM, and E Chambers, IV. 1993. Relating mea-surements of sensory properties to consumer accep-tance of meat products. Food Technol, 47(11), pp.128-31, 134.National Marine Fisheries Service. http://www.nmfs.noaa.gov/trade/default.html.National Research Council. 1988. Consumer concernsand animal product options. In: National ResearchCouncil, editors. Designing Foods. Washington, DC:National Academy Press, pp. 63-97.Pangborn, RM. 1964. Sensory evaluation of foods: Alook backward and forward. Food Technol, 18(9),pp. 63-7.Pangborn, RM. 1979. Physiological and psychologicalmisadventures. Sensory measurement or the croco-diles are coming. In: Johnsen, MR, editor. SensoryEvaluation Methods for the Practicing FoodTechnologists. Chicago, Illinois: Inst Food Technol,Pangborn, RM. 1989.The evolution of sensory scienceand its interaction with IFT. Food Technol, 43(9),pp.248-56,307.Peryam, DR. 1990. Sensory evaluation-the earlydays. FoodTechnol, 44(1),pp. 86-8, 91.Peryam, DR, and FJ Pilgrim. 1957. Hedonic scalemethod of measuring food preferences. Food Tech-nol, 11(9),pp. 9-14.Platt, W. 1931. Scoring food products. Food Ind, 3, pp.108.Price, JF, and BS Schweigert. 1987. Introduction. In:Price, JF, and BS Schweigert, editors. The Scienceof Meat and Meat Products. 3rd ed. Westport,Connecticut: Food and Nutrition Press, Inc., pp.1-9.Ramirez, G, G Hough, and A Contarini. 2001.Influence of temperature and light exposure onp. 210-211.
24 Part 11:Sensory Attributes of Muscle Foodssensory shelf-life of a commercial sunflower oil. JFood Quality, 24, pp. 195-204.Schilling, MW, JK Schilling, JR Claus, NG Marriott,SE Duncan, and H Wang. 2003. Instrumental tex-ture assessment and consumer acceptability ofcooked broiler breasts evaluated using a geometri-cally uniform-shaped sample. J Musc Foods, 14,pp. 11-23.Sidel, JS, H Stone, and J Bloomquist. 1981. Use andmisuse of sensory evaluation in research and qualitycontrol. J Dairy Sci, 64, pp. 1296-1302.Stone, H, BJ McDermott, and JL Sidel. 1991. The im-portance of sensory analysis for the evaluation ofquality. FoodTechnol, 45(6),pp. 88, 90, 92-5.Stone, H, and JL Sidel. 1998. Quantitative descriptiveanalysis: developments, applications and the future.Food Technol, 52(8),pp. 48-52.Stone, H, and JS Sidel. 1993. Sensory EvaluationPractices. 2nd ed. Orlando, Florida: Academic Press,p. 327.Stone, H, JS Sidel, S Oliver, A Woolsey, and RCSingleton. 1974. Sensory evaluation by quantitativedescriptive analysis. Food Technol, 28(1l),pp. 24-34.Szczesniak,AS. 1963.Classification of textural charac-teristics. J Food Sci, 28, pp. 385-9.Szczesniak, AS, BJ Loew, and EZ Skinner. 1975.Consumer texture profile technique. J Food Sci, 40,pp. 1253-6.
26 Part 11:Sensory Attributes of Muscle Foods(especiallythe tail and fins) (Kentouriet al. 1995,Linet al. 1998). In the case of farmed salmon, too, feed-ing fish with carotenoid pigments is regarded as themost important management practice for marketing(Moe 1990) because without them, flesh and skincolor would be less visually attractive, and thereforewould be less valued as a food (Baker 2002).Food technologists, especially those concernedwith the meat industry, have a special interest in thecolor of food for several reasons-first, because ofthe need to maintain a uniform color throughoutprocessing; second,to prevent any external or inter-nal agent from acting on the product during its pro-cessing, storage, and display; third, to improve oroptimize a product’s color and appearance; and,lastly, to attempt to bring the product’s color intoline with what the consumer expects. Put simply, thecolor of meat is determined by the pigments presentin it. These can be classified into four types: (1) bio-logical pigments (carotenes and hemopigments),which are accumulated or synthesized in the organ-ism antemortem (Lanari et al. 2002); (2) pigmentsproduced as a result of damage during manipulationor inadequate processing conditions; (3) pigmentsproduced postmortem (through enzymatic or nonen-zymatic reactions) (Montero et al. 2001, Klomklaoet al. 2006);and (4) pigments resulting from the ad-dition of natural or artificial colorants (Fernandez-Lopez et al. 2002).As a quality parameter, color has been widely stud-ied in fresh meat (MacDougall 1982, Cassens et al.1995, Faustman et al. 1996) and cooked products(Anderson et al. 1990, Fernandez-Ginks et al. 2003,Fernandez-Lopez et al. 2003). However, dry-curedmeat products have received less attention (Pkrez-Alvarez 1996, Pagan-Moreno et al. 1998, Aleson etal. 2003) because in this type of product, color forma-tion takes place during the different processing stages(Pkrez-Alvarez et al. 1997, Fernandez-Lopez et al.2000);recently, a new heme pigment has been identi-fied in this type of product (Parolari et al. 2003,Wakamatsu et al. 2004a,b). From a practical point ofview, color plays a fundamental role in the animalproduction sector, especially in meat production (beefand poultry,basically) (Zhouet al. 1993,Esteve 1994,Verdoes et al. 1999, Irie 2001), since in many coun-tries of the European Union (e.g.,Spain and Holland)paleness receives a wholesale premium.For fish, skin and flesh discoloration is a very im-portant problem, especially in highly appreciatedspecies. Since the skin and flesh color must be veryvivid, many efforts have been directed at improvingcolor, mainly through dietary control (carotene-en-riched diets) (Fujita et al. 1983,Mori 1993).Withoutthese pigments, the aquaculture industry would findit hard to undertake the production of some speciesbecause fish demand is driven through consumer de-mand for quality products (Baker 2002). In fish,consumer preference is often influenced by bodypigmentation. Fish flesh color is an important qual-ity parameter for most farmed fish, especially withsalmonids (salmon, rainbow trout), (Francis 1995,Hyun et al. 1999),in which the pink or red color offillets is an important feature (Sigurgisladottir et al.1994, Sigurgisladottir et al. 1997). For example, auniform red color in rainbow trout is considered toindicate a high-quality product and is a reason for itsacceptability, while for the tuna fish industry, it isvery important to avoid discoloration in fresh andprocessed meat and to increase its shelf life(Goodrick et al. 1991, Tze et al. 2001). Fish nutri-tion has an important impact on several parametersthat directly influence the quality of fish, some ofwhich are color and appearance. The color ofsalmonid flesh is one of the most important qualityparameters because consumers have a preference forred- or pink-colored products in the case ofsalmonids. This is the reason for using carotenoidsin aquaculture.CHEMICALAND BIOCHEMICALASPECTS OF MUSCLE-BASEDFOOD COLOROf the major components of meat, proteins are themost important since they are only provided by es-sential amino acids,which are very important for theorganism’s correct functioning; proteins also make atechnological contribution during processing, andsome are responsible for such important attributes ascolor. These are the so-called chromoproteins, andthey are mainly composed of a porphyrinic groupconjugated with a transition metal, principally ironmetalloporphyrin, which forms conjugation com-plexes (heme groups) (Whitaker 1972) that are re-sponsible for color.However,carotenes and caroteno-proteins (organic compounds with isoprenoid-typeconjugated systems) exist alongside chromoproteinsand also play an important part in meat color. Thereare also some enzymatic systems whose coenzymes
4 Chemical and BiochemicalAspects of Color in Muscle Foods 27or prosthetic groups possess chromophoric proper-ties (peroxidases, cytochromes, and flavins) (Faust-man et al. 1996). However, their contribution tomeat color is slight. Below, the principal characteris-tics of the major compounds that impart color tomeat are described.CAROTENESCarotenes are responsible for the color of beef fat,poultry meat and skin, fish, and shellfish; in the lasttwo cases, these are of great economic importance.The color of the fat is also important in carcass grad-ing. Furthermore, carotenoids can be used as muscle-based food coloring agents (Verdoes et al. 1999).Animportant factor to be taken into account with thesecompounds is that they not synthesized by the liveanimal but are obtained by assimilation (Pkrez-Alvarez et al. 2000), for instance, in the diet.Salmonids, for example, obtain carotenes in the wildin their preys, but in intensive fish culture,carotenoids must be added to the diet. Farmed fish,especially colored fish (salmon and rainbow trout,for example), are now a major industry. For exam-ple, Norway exports a great part of its salmon pro-duction. Carotenoid pigments have been used inaquafeed for many years in order to impart the de-sired flesh color in farmed salmonids (Baker 2002).Astaxanthin has been the main flesh-coloring pig-ment of choice in most trout and salmon farming in-dustries. The type of carotene used in animal feed isvery important because the fish farmer may find thatpigmentation takes on a heterogeneous appearance,which is contrary to general consumer acceptance(Yanar et al. 2006). The preferred pigments used inthe Canadian aquaculture industry are synthetic can-thaxanthin (Cx) and synthetic astaxanthin (Ax)(Higgs et al. 1995). In fats, the fatty acid composi-tion can affect their color. When the ratio of cis-monounsaturated to saturated fatty acids is high, thefat exhibits a greater yellow color (Zhou et al. 1993).In the case of the carotenes present in fish tissues,these come from the ingestion of zooplankton, algae,and crustacean wastes (Ostemeyer and Schmidt2004), and the levels are sometimes very high. Thisis possible because fish have the capacity to trans-port and deposit this pigment to specific sites in theirmuscles (Baker 2002). The deposition of Ax is higherin dark muscle than in light muscle (Ingemansson etal. 1993).The shells of many crustaceans, for exam-ple, lobster (Panilurus argus), also contain thesecompounds. Carotenoids have been extracted fromcrustacean wastes with organic solvents, but inmany of the methods pigment degradation occurs(Charest et al. 2001).The pigments responsible for color in fish, partic-ularly salmonids (trout and salmon, among others),are Ax and Cx, although they are also present in tu-nids and are one of the most important natural pig-ments of marine origin. In the case of shellfish, theircolor depends on the so-called carotenoproteins,which are proteins with a prostetic group that maycontain various types of carotene (Minguez-Mosquera 1997),which are themselves water solu-ble (Shahidi and Matusalach-Brown 1998). Henmiand coworkers (199Oa) reported that carotenoid-protein interaction in the salmon muscle is weak,and that Ax and Cx have a trans configuration invivo. Henmi and coworkers (199Ob) also reportedthat the actomyosins from salmonids showed ahigher affinity for ketocarotenoids than those ofother fish, except common mackerel. These authorsalso described correlations between the surface hy-drophobicity of actomyosins and the combination ofAx and/or canthaxanthin with actomyosins. From achemical point of view, astaxanthin or canthaxan-thin bind via a beta-ionone ring to a hydrophobicbinding site on actomyosin; the hydroxyl and ketoend groups of the beta-end group of carotenoids in-tensify binding to actomyosin. Salmon actomyosinforms complexes with free Ax, astaxanthin mono-ester, canthaxanthin, echinenone, zeaxanthin, andbeta-carotene, but not astaxanthin diester (in whicha long-chain fatty acid residue may cause steric hin-drance). The lipids in the actomyosin complex haveno effect on the binding of carotenoids (Henmi et al.1989). They are distributed in different amounts inthe flesh, head, and carapace of crustaceans, for ex-ample, astaxanthin and its esters are the majorcarotenoids found in the extracts from differentspecies of shrimp (Penaeus monodon, Penaeus indi-cus, Metapenaeus dobsonii, Parapen aeopsis stylif-era) (Sachindra et al. 2005a), but there are differenttypes of carotene, depending on whether the crus-taceans are marine or fresh water (Sachindra et al.2005b). Another difference is that the concentrationof unsaturated fatty acids in its carotenoid extractswas found to be higher than that of saturated fattyacids. In raw muscle, the main carotenoid concen-tration was strongly correlated with some color
28 Part 11:Sensory Attributes of Muscle Foodsattributes (hue, chroma, and lightness) (Choubert etal. 1992). Torrisen and coworkers (1989) reportedthat a level of 4 milligrams per kilogram (mg/kg) infish fillets is regarded as a minimum acceptablecarotenoid concentration in marketable-farmedsalmon. Sex also affects carotene concentration: fe-male muscles, which contain much more carotenoid,are more strongly colored than male muscles (Norrisand Cunningham 2004).As suggested by Torrisenand coworkers (1989),therate of carotenoid deposition in salmonids is curvilin-ear throughout the life of the fish.As the growth rate isobviously under strong genetic control, the geneticcorrelation between the growth rate and color is high.It must be taken into account that carotenoids migratefrom the muscle to the gonads. Carotene type deposi-tion in salmonid species differs; for example, Ax ismore efficiently deposited than Cx in rainbow trout(Store-bakken and Choubert 1991, Torrissen 1986),but this pattern is not the same for Atlantic salmon.These differences may be due to genetic backgroundandor environment (Baker 2002). Choubert et al.(1997) reported that in rainbow trout there is an un-equal distribution of carotenoids so that the color ofthe muscle lightens from the head toward the tail andfrom the midline of the fish towardthe dorsal and ven-tral externalarea of the fish.From a chemical point of view, carotenoids areorganic molecules that contain a conjugated carbon-carbon double bond system,which is responsible fortheir color. But this can be a problem during proces-sing, because a high number of conjugated doublebonds may be subject to oxidation, which can leadto discoloration of the carotenoids (Liaaen-Jensen1971, Choubert and Baccaunaud 2006). As carot-enoids are lipid soluble compounds, it might bethought that increasing dietary fat would increasecarotene absorption and deposition, but this is notnecessarily the case for all salmonids. The retentionof carotenoids in the flesh is relatively poor, withonly 10-18% of pigment obtained from the diet be-ing retained (Nickel1 and Bromage 1998).Astaxanthin can be found in its free, mono-, or dies-terified forms. In processed shrimps, eicosapen-taenoic acid (EPA) and docosahexaenoic acid(DHA) are the principal fatty acids esterified withthe portion of astaxanthin linked to chitin in thecarapace (Guillou et al. 1995). p-carotene and Axare fat-soluble pigments found in squid oil. How-ever, technological processes, such as refining, canremove Ax completely (Hwei and Min 1994).In fish-derived products, the carotene content haspreviously been used as a quality parameter on itsown; however, it has been demonstrated that this isnot appropriate, and that other characteristics mayinfluence color (Little et al. 1979). The carotenecontent and its influence on color is perhaps one ofthe characteristics that has received most attention(Swatland 1995). In the case of meat, especiallybeef, an excess of carotenes may actually lower thequality (Irie 2001), as occurs sometimes when clas-sifying carcasses. The Japanese system for beef car-cass classification identifies acceptable fats as white,slightly off-white, or slightly reddish white in color,while pink-yellowish and dark yellow are unaccept-able (Irie 2001). It is precisely the carotenes that areresponsible for these last two colorations. However,in other animal species, such as chicken (Castanedaet al. 2005), the opposite effect is observed, since ahigh carotene (xantophile) concentration is muchappreciated by consumers (Esteve 1994),yellow be-ing associated with traditional or “home-reared”feeding (Pkrez-Alvarez et al. 2000). The use of thecarotenoid canthaxanthin as a coloring agent inpoultry feeds is designed to result in the desired col-oration of poultry meat skins. The carotenoids usedinclude citranaxanthin, capsanthin, and capsorubin,but Cx shows superior pigmenting properties andstability during processing and storage (Blanch1999). To improve its color and brilliance, 0.004-0.04 weight percent (wt%) proanthocyanidin isadded to fish feed containing carotenoids (Sakiura2001). For rainbow trout carotenoid concentrationscould be 10.7 or 73 parts per million (ppm) Cx, or47 or 53 ppm Ax.HEMOPROTEINSOf the hemoproteins present, postmortem in themuscle, myoglobin (Mb) is the one mainly responsi-ble for color, since hemoglobin (Hb) arises from thered cells that are not eliminated during the bleedingprocess and are retained in the vascular system, ba-sically in the capillaries (incomplete exsanguina-tion; the average amount of blood remaining in meatjoints is 0.3%) (Warris and Rodes 1977).However,the contribution of red cells to color does not usuallyexceed 5% (Swatland 1995).There is wide variationin the amounts of hemoglobin from muscle tissue of
4 Chemical and BiochemicalAspects of Color in Muscle Foods 29bled and unbled fish. Myoglobin content is minimalcompared with the hemoglobin content in fish lightmuscle and white fish whole muscle. Hemoglobinmade up 65 and 56% by weight of the total hemeprotein in dark muscle from unbled and bled fish, re-spectively (Richards and Hultin 2002). Myoglobin,on average, represents 1.5% by weight of the pro-teins of the skeletal muscle, while Hb representsabout 0.5%, the same as the cytochromes and flavo-proteins combined. Myoglobin is an intracellular(sarcoplasmic) pigment apparently distributed uni-formly within muscles (Ledwar 1992, Kanner1994). It is red in color and water soluble, and it isfound in the red fibers of both vertebrates and inver-tebrates (Knipe 1993, Park and Morrisey 1994),where it fulfills the physiological role of interveningin the oxidative phosphorylization chain in the mus-cle (Moss 1992).STRUCTUREOF MYOGLOBINStructurally, Mb can be described as a monomericglobular protein with a very compact, well-orderedstructure that is specifically, almost triangularly,folded and bound to a heme group (Whitaker 1972).It is structurally composed of two groups: a pro-teinaceous group and a heme group. The proteingroup has only one polypeptidic chain composed of140-160 amino acid residues, measuring 3.6nanometer (nm) and weighing 16,900 Daltons invertebrates (Lehningher 1981). It is composed ofeight relatively straight segments (where 70% of theamino acids are found), separated by curvaturescaused by the incorporation into the chain of prolineand other amino acids that do not form alpha-helices(such as serine and isoleukin). Each segment is com-posed of a portion of alpha-helix, the largest of 23amino acids and the shortest of seven amino acids,all dextrogyrating. Myoglobin’s high helicoidal con-tent (forming an ellipsoid of 44 X 44 X 25 a)andlack of disulphide bonds (there is no cysteine) makeit an atypical globular protein. The absence of thesegroups makes the molecule highly stable (Whitaker1972). Although the three-dimensional structureseems irregular and asymmetric, it is not totally an-archic, and all the molecules of Mb have the sameconformation. One very important aspect of the pro-tein part of Mb is its lack of color. However, thevariations presented by its primary structure and theamino acid composition of the different animal andfish species destined for human consumption are thecause of the different colorations of meat and theirstability when the meats are displayed in the sameretail illumination conditions (Lorient 1982, Lee etal. 2003). The heme group of Mb (asin Hb and otherproteins) is, as mentioned above, a metallopor-phyrin. These molecules are characterized by theirhigh degree of coloration as a result of their conju-gated cyclic tetrapyrrolic structure (Kalyanasun-daram 1992). The heme group is composed of acomplex, organic annular structure, protoporphyrin,to which an iron atom in ferrous state is united (Fe11).This atom has six coordination bonds, four withthe flat protoporphyrin molecule (forming a flatsquare complex) and two perpendicular to it. Thesixth bond is open and acts as a binding site for theoxygen molecule.Protoporphyrin is a system with a voluminous flatring composed of four pyrrolic units connected bymethyl bridges (=C-).The Fe atom, with a coordi-nation number of 6, lies at the center of thetetrapyrrol ring and is complexed to four pyrrolic ni-trogens. The heme group is complexed to thepolypeptidic chain (globin) through a specific histi-dine residue (imadazolic ring) occupying the fifthposition of the Fe atom (Davidson and Henry 1978).The heme group is bound to the molecule by hydro-gen bridges, which are formed between the propy-onic acid side chains and other side chains. Otheraromatic rings exist near, and almost parallel to theheme group, which may also form pi (n)bonds(Stauton-West et al. 1969).The Hb contains a porphyrinic heme group identi-cal to that of Mb and equally capable of undergoingreversible oxygenation and deoxygenation. Indeed,is functionally and structurally paired with Mb, andits molecular weight is four times greater since itcontains four peptidic chains and four heme groups.The Hb, like Mb, has its fifth ligand occupied by theimidazol group of a histidine residue, while the sixthligand may or may not be occupied. It should bementioned that positions 5 and 6 of other hemopro-teins (cytochromes) are occupied by R groups ofspecific amino acid residues of the proteins andtherefore cannot bind to oxygen ((I2), carbonmonoxide (CO), or cyanide (CN-),except a3,which,in its biological role, usually binds to oxygen.One of the main differences between fish andmammalian Mb is that fish Mb have two distinctendothermic peaks, indicating multiple states of
30 Part 11:Sensory Attributes of Muscle Foodsstructural unfolding, whereas mammalian Mb fol-loweda two-stateunfoldingprocess.Changesin alpha-helix content and tryptophan fluorescence intensitywith temperature are greater for fish Mb than formammalian Mb. Fish Mb shows labile structuralfold-ing, suggesting greater susceptibilityto heat denatura-tion than that of mammalian Mb (Saksitet al. 1996).The helical contents of frozen-thawed Mb werepractically the same as those of unfrozen Mb, re-gardless of pH. Frozen-thawed Mb showed a higherautoxidation rate than unfrozen Mb. During freezingand thawing, Mb suffered some conformationalchanges in the nonhelical region, resulting in ahigher susceptibility to both unfolding and autoxida-tion (Chow et al. 1989). In tuna fish, Mb stabilityfollowed the order bluefin tuna (Thunnus thymus)> yellowfin tuna (Thunnus albacares) > bigeyetuna (Thunnus obesus); autoxidation rates were inthe reverse order. The pH dependency of Mb fromskipjack tuna (Katsuwonuspelamis) and mackerel(Scomberscombrus) were similar. Lower Mb stabil-ity was associated with higher autoxidation rates(Chow 1991).CHEMICALPROPERTIESOF MYOGLOBINThe chemical properties of Mb center on its abilityto form ionic and covalent groups with other mole-cules. Its interaction with several gases and waterdepends on the oxidation state of the Fe of the hemegroup (Fox 1966),since this may be in either its fer-rous (Fe 11) or its ferric (Fe 111) state. Upon oxida-tion, the Fe of the heme group takes on a positivecharge (Kanner 1994)and, typically, binds with neg-atively charged ligands, such as nitrites, the agentsresponsible for the nitrosation reactions in curedmeat products.When the sixth coordination ligand is free Mb isusually denominated deoxymyoglobin (DMb),which is purple in color. However, when this site isoccupied by oxygen, the oxygen and the Mb form anoncovalent complex, denominated oxymyoglobin(OMb), which is cherry or bright red (Lanari andCassens 1991).When the oxidation state of the ironatom is modified to the ferric state and the sixth po-sition is occupied by a molecule of water, the Mb isdenominated metmyoglobin (MMb), which isbrown. There are several possible causes for MMbgeneration, and these may include the ways in whichtunids, meat, and meat products are obtained, trans-formed, or stored (MacDougall 1982, Lee et al.2003, Mancini et al. 2003). Among the most impor-tant factors are low pH, the presence of ions, andhigh temperatures during processing (Osborn et al.2003); the growth and/or formation of metabolitesfrom the microbiota (Renerre 1990);the activity ofendogenous reducing enzymes (Arihara et al. 1995,Osborn et al. 2003); and the levels of endogenous(Lanari et al. 2002) or exogenous antioxidants, suchas ascorbic acid or its salts, tocopherols (Irie et al.1999), or plant extracts (Xin and Shun 1993,Fernandez-Lopez et al. 2003, Sanchez-Escalante etal. 2003). The pH, which may be altered dependingon postslaughter metabolism and on ingredient addi-tion, can affect the stability of the central iron atomin myoglobin and hemoglobin. At high pH, theheme iron is predominantly in the Fez+ state; lowpH accelerates Fez+ conversion to Fe3+ (Zhu andBrewer 2002, 2003). While oxygen can bind to Fez+only, many other ligands (CN, nitric oxide [NO],CO) can bind to either Fez+or Fe3+so producing avariety of colors. This change in the oxidation stateof the heme group will result in the group being un-able to bind with the oxygen molecule (Arihara et al.1995). DMb is able to react with other molecules toform colored complexes, many of which are of greateconomic relevance for the meat industry. The mostcharacteristic example is the reaction of DMb withnitrite, since its incorporation generates a series ofcompounds with distinctive colors: red in dry-curedmeat products or pink in heat-treated products. Theproducts resulting from the incorporation of nitriteare denominated cured, and such products are ofenormous economic importance worldwide (Pkrez-Alvarez 1996). The reaction mechanism is based onthe propensity of nitric oxide (NO, generated in thereaction of nitrite in acid medium, readily gives upelectrons) to form strong coordinated covalentbonds; it forms an iron complex with the DMb hemegroup independent of the oxidation state of the hemestructure. The compound formed after the nitrifica-tion reaction is denominated nitrosomyoglobin(NOMb). As mentioned above, the presence of re-ducing agents such as hydrogen sulfide acid (HzS)and ascorbates lead to the formation of undesirablepigments in both meat and meat products. Thesegreen pigments are called sulphomyoglobin (SMb)and colemyoglobin (ColeMb), respectively, and areformed as a result of bacterial activity and an excessof reducing agents in the medium. The formation of
4 Chemical and BiochemicalAspects of Color in Muscle Foods 31SMb is reversible, but that of ColeMb is an irre-versible mechanism, since it is rapidly oxidized be-tween pH 5 and 7, releasing the different parts of theMb (globin, iron, and the tetrapyrrolic ring).From a chemical point of view, it should be bornein mind that the color of Mb, and therefore of themeat or meat products, not only depends on the mol-ecule that occupies the sixth coordination site, butalso on the oxidation state of the iron atom (ferrousor ferric), the type of bond formed between the li-gand and the heme group (coordinated covalent,ionic, or none),and the state of the protein (native ordenatured form), not to mention the state of the por-phyrin of the heme group (intact, substituted, or de-graded) (Pkrez-Alvarez 1996).During the heat treatment of fish flesh, the aggre-gation of denatured fish proteins is generally accom-panied by changes in light-scattering intensity.Results demonstrate changes in relative light-scattering intensity can be used for studying struc-tural unfolding and aggregation of proteins underthermal denaturation (Saksit et al. 1998).When fattyfish meat like Trachurusjaponicus was heat treated,the MMb content increased linearly, and the per-centages of denatured myoglobin and apomyoglobinincreased rapidly when mince was exposed to heat,but when the temperature reached 60°C the linearitywas broken. The results indicated that MMb colorstability was higher than that of Mb and that thethermal stability of heme was higher than that ofapomyoglobin (Hui et al. 1998). Both Mb and fer-rous iron accelerated the lipid oxidation of cooked,water-extracted fish meat. EDTA (ethylenedi-aminetetraacetic acid) inhibited the lipid oxidationaccelerated by ferrous iron, but not that acceleratedby Mb. Also, with cooked, nonextracted mackerelmeat, EDTA noticeably inhibited lipid oxidation.Nonheme iron catalysis seemed to be related in partto lipid oxidation in cooked mackerel meat. The ad-dition of nitrite in combination with ascorbate re-sulted in a marked inhibition of lipid oxidation inthe cooked mackerel meat. From these results, it waspostulated that nitric oxide ferrohemochromogen,formed from added nitrite and Mb (present in themackerel meat) in the presence of a reducing agent,possesses an antioxidant activity, which is attribut-able in part to its function as a metal chelator(Ohshima et al. 1988).Tuna fish meat color can be improved when theflesh is treated or packaged with a modified atmos-phere in which CO is included. Normally, the rate ofpenetration of CO or carbon dioxide (CO,) in fishmeat such as tuna, cod, or salmon, under differentpackaging conditions, is measured by monitoringpressure changes in a closed constant volume cham-ber with constant volume and temperature. Alterna-tively, however, the specific absorption spectrum ofcarboxymyoglobin (MbCO), within the visiblerange, can be obtained and used as an indicator ofMbCO formation. Mb extracts from tuna muscletreated with CO exhibited higher absorbance at 570than at 580 nm. Therefore, the relationship betweenabsorbance at 570 nm and absorbance at 580 nmcould be used to determine the extent of CO penetra-tion of tuna steaks placed in a modified atmospherein which CO was included. The penetration of COinto tuna muscle was very slow.After approximately1-4 hours, CO had penetrated 2-4 mm under thesurface, and after 8 hours, CO had penetrated 4-6mm (Chau et al. 1997).In products with added nitrite or nitrate the com-plex nitrosylmyoglobin (MbFeNO) is the maincontributor to the characteristic color of cookedcured ham, and brine-cured and dry-cured meatproducts. Meat and meat products without nitrite/nitrate addition will normally attain a dull browncolor or a gray color in heated products, which influ-ences consumer acceptance negatively (Adamsen etal. 2005). In dry-cured meat products such as Parmaham produced without nitrite or nitrate addition, thecharacteristic bright red color (Wakamatsu et al.2004a) is caused by Zn-protoporphyrin IX (ZPP)complex, a heme derivative. Adamsen et al. (2005)showed that the use of nitrite as a curing ingredientinhibits the formation of Zn-pp. In the same workthe author described that this color compound is pre-sent in other meat products like Iberian ham, al-though in a lower concentration.Virgili et al. (1999) reported that this color maybe due to the action of low-molecular weight com-pounds containing electron-donating atoms, formedduring maturation, in particular basic peptides oramino acids resulting from an external proteolysis,which may play a role as Fe ligands in Mb.Wakamatsu and coworkers (2004b) reported thatanaerobic conditions favor the formation of Zn-ppand that endogenous enzymes as well as microor-ganisms may also be involved. There are several hy-potheses that try to explain the formation of thiscompound. Wakamatsu et al. (2004b) described
32 Part 11:Sensory Attributes of Muscle Foodsthree possible substitution patterns: (i) a nonenzy-matic reaction in which Zn(I1) substitutes Fe(I1) un-der anaerobic conditions, with concomitant dissoci-ation of the heme; (ii) a bacterial enzymaticreaction, whereby bacterial growths naturally de-grade the meat proteins including the pigment; or(iii) an enzymatic reaction where an endogenousferrochelatase interchanges the two metals. How-ever,Adamsen et al. (2005) described this process ashaving the three following mechanisms to explainthe metal substation: (i) a nonenzymatic enzymaticreaction driven by binding of iron in the high chlo-ride meat matrix; (ii) a bacterial enzymatic reaction;or (iii) an endogenous enzymatic reaction.Also spectroscopic studies of Parma ham duringprocessing revealed a gradual transformation ofmuscle myoglobin, initiated by salting and continu-ing during aging. Using electron spin resonancespectroscopy, Moller and coworkers (2003) haveshown that the Parma ham pigment is different fromMbFe(I1)NO and is not a nitric oxide complex suchas that found in brine-cured ham and SpanishSerrano hams. These authors also establish that theheme moiety is present in the acetone-water extractand that Parma ham pigment is gradually trans-formed from a myoglobin derivative into a nonpro-tein heme complex, which is thermally stable in anacetone-water solution. Adamsen et al. (2003) alsodemonstrated that the heme moieties of Parma hampigments have antioxidative properties. Pigmentsbecame increasingly lipophilic during processing,suggesting that a combination of drying and matur-ing yields a stable red color (Parolari et al. 2003).CYTOCHROMESCytochromes are metalloproteins with a prosteticheme group, whose putative role in meat colorationis undergoing revision (Boyle et al. 1994, Faustmanet al. 1996). Initially, they were not thought to play avery important role (Ledwar 1984). These com-pounds are found in low concentrations in the skele-tal muscle, and in poultry, they do not representmore than 4.23% of the total hemeoproteins present(Pikul et al. 1986). It has now been shown that therole of cytochrome (especially its concentration) inpoultry meat color is fundamental, when the animalhas been previously exposed to stress (Ngoka andFroning 1982, Pikul et al. 1986). Cytochromes aremost concentrated in cardiac muscle so that whenthis organ is included in meat products, heart contri-bution to color,not to mention the reactions that takeplace during elaboration processes, must be takeninto consideration (Pkrez-Alvarez et al. 2000).COLOR CHARACTERISTICSOF BLOODAnimal blood is little used in the food industry be-cause of the dark color it imparts to the products towhich it is added. For solving the negative aspects ofblood incorporation, specifically food color-relatedproblems, several different processes and meanshave been employed, but they are not always com-pletely satisfactory. The addition of 12% bloodplasma to meat sausages leads to pale-colored prod-ucts. Addition of discolored whole blood or globin(from which the hemoglobins heme group has beeneliminated) has also been used to address colorproblems. Natural red pigments can be obtainedfrom blood without using coloring agents such as ni-trous acid salts; these pigments have zinc protopor-phyrin as the metalloporphyrin moiety and can beused to produce favorably colored beef products,whale meat products, and fish products (includingfish pastes) (Numata and Wakamatsu 2003). Therewas wide variation in amounts of haemoglobin ex-tracted from the muscle tissue of bled and unbledfish, and the residual level in the muscle of bled fishwas substantial. Myoglobin content was minimal ascompared with hemoglobin content in mackerellight muscle and trout whole muscle. Hemoglobinmade up 65 and 56% by weight of the total hemeprotein in dark muscle from unbled and bled mack-erel, respectively. The blood-mediated lipid oxida-tion in fish muscle depends on various factors, in-cluding hemoglobin concentration, hemoglobintype, plasma volume, and erythrocyte integrity(Richards and Hultin 2002). The presence of blood,Hb, Mb, Fe", Fe+3,or Cu" can stimulate lipid ox-idation in the fillets of icefish (Rehbein and Orlick1990, Richards and Li 2004). Kanner and coworkers(1987) reported that hemoglobin, myoglobin, cop-per, and iron have the potential to promote lipid oxi-dation in muscle foods. Since iron can be releasedfrom hemoglobin during storage, it is difficult to as-certain whether the intact heme protein, dissociatedheme, or released iron is responsible for the bulk of
4 Chemical and BiochemicalAspects of Color in Muscle Foods 33lipid oxidation that occurs during storage. For thisreason, Svingen and coworkers (1979) used the termlow molecular weight iron instead of free iron sinceiron binds to other low molecular weight com-pounds to gain solubility and hence potential reac-tivity. Ferrous and ferric forms of iron can promotelipid oxidation processes (Gutteridge 1986,Tadoliniand Hakim 1996). Iron shows a high reactivity withreactants such as hydrogen peroxide and lipid per-oxides (Kanner and Hare1 1987).Mitochondria are a source of reactive oxygenspecies that could confound lipid oxidation reac-tions due to added hemoglobin. During fish proces-sing (e.g., tuna fish), the loss of redness can be agood indicator that lipid oxidation processes medi-ated by hemoglobin (Hb) are progressing. Just afterdeath, Hb in muscle tissue is primarily in the re-duced state (i.e., oxyhemoglobin [oxyHb] and de-oxyhemoglobin [deoxyHb]).This mixture of oxyHb and deoxyHb has a redcolor.With increased postmortem aging, Hb autoox-idizes to methemoglobin [metHb],a brown pigment.MetHb is considered more prooxidative than re-duced Hb due to its less tightly bound heme groupand its reactivity with hydrogen peroxide and lipidperoxides to form hypervalent Hb catalysts (Everseand Hsia 1997).From a technological point of view, during meator fish processing, rapid chilling may alter oxygensolubility in tissues resulting in less available oxy-gen to oxygenate either oxymyoglobin or hemoglo-bin. The conversion of oxymyoglobin to metmyo-globin, which is brown and unattractive, occursunder conditions of very low oxygen tension as well(Nicolalde et al. 2005).Field and coworkers (1978) describe how bonemarrow is high in hemoglobin, while muscle has ahigh myoglobincontent.As with other meats, its colorand hemoglobin stability depend on packaging andstorage conditions. Good temperature control andmodified atmosphere packaging (MAP) with highoxygen atmospheres (80%) are often used to extendboth microbiologicaland color shelf life (Nicolaldeetal. 2005).FAT COLORFrom a technological point of view, fat fulfills sev-eral functions, although, regarding color, its princi-pal role is in the brightness of meat products. Pro-cesses such as “afinado” during the elaboration ofdry-cured ham involve temperatures at which fatmelts so that it infiltrates the muscle mass and in-creases its brilliance (Sayas 1997). When the fat isfinely chopped, it “dilutes”the red components ofthe color, thus decreasing the color intensity of thefinished product (Pkrez-Alvarez et al. 2000). How-ever, fats do not play such an important role in finepastes since, after emulsification, the fat is maskedby the matrix effect of the emulsion so that it con-tributes very little to the final color. The color of fatbasically depends on the feed that the live animal re-ceived (Esteve 1994, Irie 2001). In the case ofchicken and ostrich, the fat has a “white” appear-ance (common in Europe) when the animal has beenfed with “white” cereals or other ingredients notcontaining xanthophylls, since these are accumu-lated in subcutaneous fat and other fatty deposits.However, when the same species are fed maize (richin xanthophylls), the fatty deposits take on a yellowcolor. Beef or veal fat, that is dark, hard (orsoft),ex-cessively bright, or shiny lowers the carcass and cutprice. Fat with a yellowish color in healthy animalsreflects a diet containing beta-carotene (Swatland1988). While fat color evaluation has traditionallybeen a subjective process, modern methods includesuch techniques as optical fiber spectrophotometry(Irie 2001). Another factor influencing fat color isthe concentration of the Hb retained in the capillar-ies of the adipose tissues (Swatland 1995). As inmeat, the different states of Hb may influence thecolor of the meat cut. OMb is responsible for theyellowish appearance of fat, since it affects differentcolor components (yellow-blue and red-green).The different states of hemoglobin present in adi-pose tissue may react in a similar way to those inmeat so that fat color should be measured as soon aspossible to avoid possible color alterations. Whenthe Hb in the adipose tissue reacts with nitrite incor-porated in the form of salt, nitrosohemoglobin(NOHb),a pigment that imparts a pink color to fat,is generated. This phenomenon occurs principally indry-cured meat products with a degree of anatomi-cal integrity, such as dry-cured ham or shoulder(Sayas 1997).When fat color is measured, its com-position should be borne in mind since its relationwith fatty acids modifies its characteristics, makingit more brilliant or duller in appearance. The fat con-
34 Part 11:Sensory Attributes of Muscle Foodstent of the conjunctive tissue must also be borne inmind-collagen may present a glassy appearancebecause, at acidic pH, it is “swollen,”imparting atransparent aspect to the product.ALTERATIONS IN MUSCLE-BASED FOOD COLORThe color of meat and meat products may be alteredby several factors, including exposure to light(source and intensity), microbial growth, rancidity,and exposure to oxygen. Despite the different alter-ations in color that may take place, only a few havebeen studied; these include the pink color of boileduncured products, premature browning, fish skindiscoloration. and melanosis in crustaceans.PINK COLOR OF UNCUREDMEAT PRODUCTSThe normal color of a meat product that has beenheat treated but not cured is “brown,”although it hasrecently been observed that these products show ananomalous coloration (red or pink) (Hunt and Kropf1987).This problem is of great economic importancein “grilled” products since this type of color is notconsidered desirable. This defect may occur both inmeats with a high hemoprotein content, such as beefand lamb (red);and in those with a low hemoproteinconcentration, including chicken and turkey (pink)(Conforth et al. 1986). One of the principal causes ofthis defect is the use of water rich in nitrates, whichare reduced to nitrites by nitrate-reducing bacteria,which react with the Mb in meat to form NOMbmash et al. 1985). The same defect may occur inmeat products containing paprika, which accordingto Fernandez-Lopez (1998), contains nitrates that,once incorporated in the product, may be similarlyreduced by microorganisms. Conforth et al. (1991)mention that several nitrogen oxides may be gener-ated in gas and electric ovens used for cooking hamand that these nitrogen oxides will react with the Mbto generate nitrosohemopigments. CO is also pro-duced in ovens, which reacts with Mb during thermaltreatment to form a pink-colored pigment, carboy-hemochrome. It has also been described how the useof adhesives formed from starchy substances pro-duces the same undesirable pink color in cookedproducts (Scriven et al. 1987). The same anomalouspink color may be generated when the pH of themeat is high (because of the addition of egg albuminto the ingredients) (Froning et al. 1968)and when thecooking temperature during processing is too low.These conditions favor the development of a reduc-ing environment that maintains the iron of the Mb inits ferrous form, imparting a reddish/pink color (as afunction of the concentration of hemopigments) in-stead of the typical grayish brown color of heat-treated, uncured meat products.Cooking uncured meat products, such as roastbeef, at low temperatures (less than 60°C) may pro-duce a reddish color inside the product, which someconsumers may like. This internal coloring is not re-lated to the formation of nitrosopigments, but resultsfrom the formation of OMb, a phenomenon that oc-curs because there exist in the muscle MMb-reducing enzymatic systems that are activated attemperatures below 60°C (Osborn et al. 2003).Microbial growth may also cause the formation of apink color in cooked meats since these reduce theoxidoreduction potential of the product during theirgrowth. This is important when the microorganismsthat develop in the medium are anaerobes, since theymay generate reducing substances that decrease theheme iron. When extracts of Pseudomonas culturesare applied, the MMb may be reduced to Mb(Faustman et al. 1990).MELANOSISMelanosis, or blackspot, involving the appearanceof a dark, even black, color, may develop post-mortem in certain shellfish during chilled and frozenstorage (Slattery et al. 1995). Melanosis is of hugeeconomic importance since the coloration may sug-gest a priori in the eyes of the consumer that theproduct is in bad condition, despite the fact that theformation of the pigments responsible involves nohealth risk. Melanosis is an undesirable surface dis-coloration of such high value shellfish as lobstersthat takes place immediately after harvesting since itstarts with oxygen contact (Lopez-Caballero et al.2006). Blackspot is caused by enzymic formation ofthe precursors of phenolic pigments (Williams et al.2003). Blackspot is a process regulated by a com-plex biochemical mechanism, whereby the phenolspresent in a food are oxidized to quinones in a seriesof enzymatic reactions caused by polyphenol oxi-dase (PPO) (Ogawa et al. 1984). This is followedby a polymerization reaction, which produces pig-
4 Chemical and BiochemicalAspects of Color in Muscle Foods 35ments of a high molecular weight and dark color.Melanosis is produced in the exoskeleton of crus-taceans, first in the head and gradually spreading to-ward the tail. Melanosis of shell and hyperdermaltissue in some shellfish, such as lobsters, has beenrelated to stage of molt, since the molting fluid isconsidered to be the source of the natural activa-tor(s) of pro-PPO.Polyphenol oxidase (catechol oxidase) can be iso-lated from shellfish cuticle (Ali et al. 1994) and isstill active during iced or refrigerated storage. Someauthors have found a connection between melanosisand microbial growth in crustaceans. Thus, colorformation (melanin) due to strains of P fragi mayoccur if prawns are not properly chilled (Chini-vasagam et al. 1998). In this respect, Lopez-Caballero et al. (2006) reported that the presence ofmicroorganisms (e.g., Proteus spp., Pseudomonas,etc.) and the H2Sproduced reacted with metals ofthe lobster shell resulting in melanosis. Sulphitescan be used to control the process (Ferrer et al. 1989,Gomez-Guillen et al. 2005), although their use isprohibited in many countries. It is well known thatthe inhibitory effect of blackspot is specific for eachspecies, requiring adequate doses and formulations(Montero et al. 2001). The effective dose of 4-hexyl-resorcinol differs depending on the physiologicalstate, season, method of application, etc., althoughthe species being treated is one of the most impor-tant of these factors. Montero et al. (2004) andLopez-Caballero et al. (2006) found that, regardlessof the season, a concentration of 0.25% 4-hexyl-resorcinol was effective in extending the shelf lifeof pink shrimp. Ficin (Taoukis et al. 1990) and 4-hexylresorcinol also functioned as a blackspot in-hibitor, alone and in combination with L-lactic acid(Benner et al. 1994).FISH SKIN DISCOLORATIONIn fish and other vertebrates, in which the pigmenta-tion of the skin can be changed by hormonal stimula-tion, the color of the background and illumination aredetermining factors for the intensity andor the pat-tern of skin fish pigmentation (Sugimoto 1997,Durayet al. 1996, Crook 1997, Healey 1999, Papoutsoglouet al. 2000, Rotllant et al. 2003). In addition, tempera-ture may also have an impact on color (FernandezandBagnara 1991).In some types of fish, especially thosewith a red skin, the color tone becomes dark immedi-ately after killing, reducing the commercial value ofthe fish. Most of the color changes in fish are oftenrelated to stress. It is generally accepted thatmelanophores play an important role in the rapidcolor change of certain fish (Fujii 1969). Thesechanges are related to hormonal (a-melanocyte-stimulating hormones) responses causing dispersionof the melanin granules in melanophores and are re-sponsible for skin darkening (Green and Baker 1991,Lamers et al. 1992, Groneveld et al. 1995,Arends etal. 2000, Burton and Vokey 2000).In the case of Red Sea Bream, the rapid skin colorchanges after killing of cultured fish is thought to bemainly due to the rapid dispersion of chromato-somes in melanophores elicited by handling andkilling stresses. Potassium ions through the nor-adrenaline pathway can induce aggregation of chro-matosomes in melanophores (Kumazawa and Fujii1984). In fish skin, besides melanophores there areother chromatophores, such as xanthophores anderythrophores, the latter mainly contributing to thered color of the fish skin.PREMATURE BROWNINGHard-to-cook patties show persistent internal redcolor and are associated with high pH (>6) rawmeat. Pigment concentration affects red color inten-sity after cooking (residual undenatured myoglo-bin), so this phenomenon is often linked to high pHdark cutting meat from older animals. Prematurebrowning is a condition in which ground beef(mince) looks well done at a lower than expectedtemperature (Warren et al. 1996). Premature brown-ing (PMB) of ground beef is a condition in whichmyoglobin denaturation appears to occur on cook-ing at a temperature lower than expected; it may in-dicate falsely that an appropriate internal core tem-perature of 71°C has been achieved (Suman et al.2004). The relationship between cooked color andinternal temperature of beef muscle is inconsistentand depends on pH and animal maturity. Increasingthe pH may be of benefit in preventing prematurebrowning, but it may increase the incidence of redcolor in well-cooked meat (cooked over an internaltemperature of 71.1"C) (Berry 1997). When pale,soft, exudative (PSE) meat was used in patty proces-sing, patties containing OMb easily exhibited pre-mature browning. One reason for this behavior isthat the percentage of Mb denaturation increased ascooking temperature rose (Lien et al. 2002).
36 Part 11:Sensory Attributes of Muscle FoodsCOLOR AND SHELF LIFE OFMUSCLE-BASEDFOODSMeat and meat products are susceptible to degrada-tion during storage and throughout the retail process.In this respect, color is one of the most importantquality attributes for indicating the state of preserva-tion in meat. Any energy received by food can initi-ate its degradation, but the rate of any reaction de-pends on the exact composition of the productOensen et al. 1998), environmental factors (light,temperature, presence of oxygen), and the presenceof additives. Transition metals such as copper andiron are very important in the oxidative/ antioxidativebalance of meat. When the free ions of these twometals interact, they reduce the action of certainagents, such as cysteine, ascorbate, and alpha-tocopherol, oxidizing them and significantly reduc-ing the antioxidant capacity in muscle (Zanardi et al.1998).Traditionally, researchers have determined thediscoloration of meat using as criterion the browncolor of the product, calculated as percent MMb(Mancini et al. 2003). These authors demonstratedthat in the estimation of the shelf life of beef or veal(considered as discoloration of the product), thediminution in the percent of OMb is a better tool thanthe increase in percentage of MMb. Occasionally,when the meat cut contains bone (especially in porkand beef), the hemopigments (mainly Hb) present inthe medulla lose color because the erythrocytes arebroken during cutting and accumulate on the surfaceof the bone hemoglobin. When exposed to light andair, the color of the Hb changes from the bright red(oxyhemoglobin [Ohb]),the characteristic of blood,to brown (methemoglobin [MHb]) or even black(Gill 1996). This discoloration basically takes placeduring long periods of storage, especially duringshelf life display (Mancini et al. 2004). This charac-teristic is aggravated if the product is kept in a modi-fied atmosphere rich in oxygen (Lanari et al. 1995).These authors also point out that the effect of bonemarrow discoloration is minimized by the effect ofbacterial growth in modified atmosphere packaging.As in the case of fresh meat, the shelf life of meatproducts is limited by discoloration (Mancini et al.2004). This phenomenon is important in this type ofproduct because they are normally displayed in illu-minated cabinets. Consequently, the possibility ofphotooxidation of nitrosomyoglobin (NOMb) needsto be taken into account.During this process, the molecule is activated be-cause it absorbs light; this may subsequently deacti-vate the NOMb and give the free electrons to theoxygen to generate MMb and free nitrite. In modelsystems of NOMb photooxidation, the addition ofsolutions of dextrose, an important component ofthe salts used for curing cooked products and inmeat emulsions, can diminish the effect of NOMbphotooxidation. When a meat product is exposed tolight or is stored in darkness, the use of ascorbic acidor its salts may help stabilize the products color.Such behavior has been described both in modelsystems of NOMb (Walsh and Rose 1956) and indry-cured meat products (e.g., longanizas, Spanishdry-fermented sausage). However, when sodiumisoascorbate or erythorbate is used in longanizasproduction, color stability is much reduced duringthe retail process (Ruiz-Peluffo et al. 1994).The discoloration of white meats such as turkey ischaracterized by color changes that go from pink-yellow to yellow-brown, while in veal and beef, thechanges go from purple to grayish brown. In turkey,it has been demonstrated that the presence or ab-sence of lipid oxidation depends on, among otherthings, the concentration of vitamin E in the tissues.The color and lipid oxidation are interrelated since ithas been seen that lipid oxidation in red and whitemuscle depends on the predominant form of catalyz-ing iron, Mb, or free iron (Mercier et al. 1998).Compared with red meat, tuna flesh tends to un-dergo more rapid discoloration during the refriger-ated storage. Discoloration due to the oxidation ofMb in red fish presented a problem, even at low tem-peratures. This low color stability might be relatedto the lower activity or poorer stability of MMb re-ductase in tuna flesh (Ching et al. 2000). Anotherreason for the low color stability is that aldehydesproduced during lipid oxidation can accelerate tunaOMb oxidation in vitro (Lee et al. 2003). Tuna fleshcould be immersed in an MMb reductase solution toextend the color stability of tuna fish. Also, the useof this enzyme can reduce MMb formation duringrefrigerated storage of tuna (Tze et al. 2001).Yellowtail (Seriola quinqueradiata) fillets stored ingas barrier film packs filled with nitrogen (Nz)andplaced in cold storage at 0-5"C, stayed fresh for 4-7days. Nz or COz packaging did not prevent discol-oration in frozen tuna fillets; better results wereachieved by thawing the frozen tuna meat in an Ozatmosphere (Oka 1989). Packaging in atmospheres
4 Chemical and BiochemicalAspects of Color in Muscle Foods 37containing 4 or 9% O2was inferior to packaging inair, as these atmospheres promoted MMb formation.Packaging in 70% O2maintained the fresh red colorof tuna dorsal muscle for storage periods less than 3days (Tanaka et al. 1996).To change the dark browncolor to a bright red color, processors sometimestreat tuna with 100% carbon monoxide (CO) duringmodified atmosphere packaging. Since Mb can reactwith CO rapidly even at low CO concentrations (Chiet al. 2001), modified atmosphere packaging with100% CO may result in high CO residues in theflesh, which may cause health problems.MICROORGANISMS ANDMUSCLE-BASEDFOOD COLORAlthough the real limiting factor in the shelf life offresh meat is the microbial load, consumers choosefresh meat according to its color. The bacterial loadis usually the most important cause of discolorationin fresh meat and meat products (sausages and othercooked products), and slaughter, cutting, and pack-aging must be strictly controlled. Bacterial contami-nation decisively affects the biochemical mecha-nisms responsible for the deterioration of meat(Renerre 1990). Is it important to take into accountthat,just as with the bacterial load, the effect of dis-coloration on meat is more pronounced in meats thatare more strongly pigmented (beef) than in less pig-mented meats such as pork and chicken (Gobantesand Oliver 2000). Another variable affecting colorstability in meat is the quantity of microorganismspresent (Houben et al. 1998); concentrations in ex-cess of 106/gram (g) have a strong effect. Althoughantioxidants, such as ascorbic acid,slow lipid oxida-tion and consequently improve color stability, thesesubstances have little effect when bacterial growth isa problem (Zerby et al. 1999).REFERENCESAdams, DC, and RT Huffman. 1972. Effect of con-trolled gas atmospheres and temperature on qualityof packaged pork. J Food Sci, 37, pp. 869-872.Adamsen, CE, JKS Moller, K Laursen, K Olsen, and LHSkibsted. 2005.Zn-porphyrin formation in cured meatproducts: Effect of added salt and nitrite. Meat Sci, inpress. Available on line at www.sciencedirect.com.Adamsen, CE, ML Hansen, JKS Moller, and LHSkibsted. 2003. Studies on the antioxidative activityof red pigments in Italian-type dry-cured ham. EurFood Res Technol, 217(3),pp. 201-206.Aleson, L, J Fernandez-Lbpez, E Sayas-Barbera, ESendra, and JA Perez-Alvarez. 2003. Utilization oflemon albedo in dry-cured sausages. J Food Sci, 68,pp. 1826-1830.Ali, MT, RA Gleeson, CI Wei, and MR Marshall. 1994.Activation mechanisms of pro-phenoloxidase onmelanosis development in Florida spiny lobster(Panulirus argus) cuticle. J Food Sci, 59(5), pp.1024-1030.Anderson, HJ, G Bertelsen, and LH Skibsled. 1990.Colour and colour stability of hot processed frozenminced beef. Result from chemical model experi-ments tested under storage conditions. Meat Sci,28(2),pp. 87-97.Arends, RJ, J Rotllant, JR Metz, JM Mancera, SEWendelaar-Bonga, and G Flik. 2000. alpha-MSHacetylation in the pituitary gland of the sea bream(Sparus aurata L.) in response to different back-grounds, confinement and air exposure. J. Endocrinol,166 (Z), pp. 427-435.Arihara, K, M Itoh, andY Kondo. 1995.Significance ofmetmyoglobin reducing enzyme system in my-ocytes. Proc. 41st Int Cong Meat Sci and Technol,San Antonio, Texas, C70, pp. 378-379.Baker, RTM. 2002. Canthaxanthin in aquafeed applica-tions: is there any risk? Trends Food Sci Technol, 12,pp. 240-243.Benner, RA, R Miget, G Finne, and GR Acuff. 1994.Lactic acid/melanosis inhibitors to improve shelf lifeof brown shrimp (Penaeus aztecus). J Food Sci,59(2),pp. 242-245.Berry, BW. 1997. Color of cooked beef patties as influ-enced by formulation and final internal temperature.Food Res Int, 30(7),pp. 473-478.Blanch, A. 1999. Getting the colour of yolk and skinright. World Poultry, 15(9),pp. 32-33.Boyle, RC, AL Tappel, AA Tappel, H Chen, and HJAndersen. 1994. Quantitation of haeme proteinsfrom spectra of mixtures. J Agric Food Chem, 42,pp. 100-104.Brewer, MS, and FK Mckeith. 1999. Consumer-ratedquality characteristics as related to purchase intent offresh pork. J Food Sci, 64, pp. 171-174.Bryhni, EA, DV Byrne, M Rmdbotten, C Claudi-Magnussen, H Agerhem, M Johansson, P Lea, and MMartens. 2002. Consumer perceptions of pork inDenmark, Norway and Sweden. Food Qua1 Pref, 13,pp. 257-266.Burton, D, and JE Vokey. 2000. The relative in vitroresponsiveness of melanophores of winter flounder
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