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  2. 2. Food Preservation Methods <ul><li>Inhibition </li></ul><ul><li>Inactivation </li></ul><ul><li>Avoid contamination </li></ul>
  3. 3. Inhibition <ul><li>low T storage </li></ul><ul><li>reduction of aw </li></ul><ul><li>decrease O2, increase CO2, vacuum </li></ul><ul><li>acidification </li></ul><ul><li>fermentation </li></ul><ul><li>freezing </li></ul><ul><li>surface coating </li></ul><ul><li>structural modification </li></ul>
  4. 4. Inactivation <ul><li>sterilization </li></ul><ul><li>pasteurization </li></ul><ul><li>radiation </li></ul><ul><li>electrifying </li></ul><ul><li>high pressure </li></ul><ul><li>blanching </li></ul><ul><li>cooking </li></ul><ul><li>frying </li></ul>
  5. 5. Avoid recontamination <ul><li>packaging </li></ul><ul><li>hygienic processing </li></ul><ul><li>hygienic storage </li></ul><ul><li>aseptic processing </li></ul>
  6. 6. Thermal processing <ul><li>pasteurization </li></ul><ul><ul><li>inactivation of vegetative cells and/or enzymes </li></ul></ul><ul><li>sterilization </li></ul><ul><ul><li>inactivation of spores </li></ul></ul><ul><li>blanching </li></ul><ul><ul><li>inactivate enzymes fruits and vegetables </li></ul></ul><ul><li>ohmic heating </li></ul><ul><ul><li>electrical conductivity for foods with 30-40% water dissolved ionic components uniform heating short processing time </li></ul></ul>
  7. 7. Cold storage <ul><li>Chilling </li></ul><ul><ul><li>slowing microbical growth </li></ul></ul><ul><ul><li>reduce enzymatic and chemical reactions </li></ul></ul><ul><ul><li>slow postharvest metabolism </li></ul></ul><ul><ul><li>reduce moisture loss </li></ul></ul><ul><li>Freezing </li></ul><ul><ul><li>slowing microbial and chemical reactions </li></ul></ul><ul><ul><li>water immobilization </li></ul></ul><ul><ul><li>reducing molecular mobility </li></ul></ul><ul><ul><li>some microbial destruction </li></ul></ul>
  8. 8. Reducing aw <ul><li>drying </li></ul><ul><li>freeze-drying </li></ul><ul><li>humectants </li></ul><ul><li>freezing </li></ul><ul><ul><li>slowing microbial and chemical reactions </li></ul></ul><ul><ul><li>water immobilization </li></ul></ul><ul><ul><li>reducing molecular mobility </li></ul></ul>
  9. 9. Fermentation <ul><li>inhibition of spoilage/pathogenic flora by beneficial microbial flora </li></ul><ul><li>consumption of substrate for biochemical/chemical reactions </li></ul><ul><li>production of antimicrobials </li></ul><ul><li>acidification </li></ul>
  10. 10. Preservatives <ul><li>acidification </li></ul><ul><ul><li>pH change </li></ul></ul><ul><ul><li>antimicrobial property </li></ul></ul><ul><li>other preservatives </li></ul><ul><ul><li>antimicrobial </li></ul></ul><ul><ul><li>antioxidant </li></ul></ul><ul><ul><li>enzyme inhibitor </li></ul></ul><ul><ul><li>control redox potential </li></ul></ul>
  11. 11. Control of redox potential <ul><li>CA/MAP </li></ul><ul><ul><li>prevent postharvest ripening </li></ul></ul><ul><ul><li>reduce microbial activity </li></ul></ul>
  12. 12. Nonthermal processing <ul><li>Irradiation </li></ul><ul><ul><li>free radical species </li></ul></ul><ul><ul><li>hydrogen, H 2 O 2 , OOH </li></ul></ul><ul><li>High pressure </li></ul><ul><ul><li>3500-10000 atm </li></ul></ul><ul><ul><li>protein damage </li></ul></ul><ul><li>Pulsed electric field </li></ul><ul><ul><li>dielectric cell membrane destruction </li></ul></ul><ul><li>Oscillating magnetic fields </li></ul><ul><li>Microwave </li></ul><ul><ul><li>thermal effect (?) </li></ul></ul>
  13. 13. Irradiation <ul><li>- nonthermal </li></ul><ul><li>- process in package, minimize contamination </li></ul><ul><li>- form of food is not a factor </li></ul><ul><li>- can replace preservatives, insecticides </li></ul><ul><li>- can be used in fresh foods </li></ul><ul><li>Canada </li></ul><ul><li>1960 – sprout control in potatoes and onions </li></ul><ul><li>1961 – insect control in wheat </li></ul><ul><li>1983 - spices </li></ul>
  14. 14. Irradiation <ul><li>Doses of irradiation </li></ul><ul><li>sprout inhibition: 0.15-0.2 kGy </li></ul><ul><li>flour disinfestations: <= 1kGy </li></ul><ul><li>spice cleaning: 5 kGy </li></ul><ul><li>parasite elimination: <=6 kGy </li></ul><ul><li>pathogen destruction: <=10 kGy </li></ul><ul><li>bacterial destruction: <=5 kGy </li></ul>
  15. 15. Irradiation <ul><li><= 10 kGy harmless to human health (UN) </li></ul><ul><li>pasteurization effect </li></ul><ul><li>need to be used in combination with refrigeration and CA/MAP </li></ul><ul><li>currently used for </li></ul><ul><li>spices, disinfestations of cereal grains, pathogen control in poultry, trichinosis control in fresh pork, tropical fruits </li></ul>
  16. 16. Chilling <ul><li>storage at T > T fp ( -1 ) - ( +10 C ) </li></ul><ul><li>chilling injury near T fp </li></ul><ul><li>texture degradation in vegetables </li></ul><ul><li>cold shortening of muscle foods, staling of bread </li></ul>
  17. 17. Freezing <ul><li>small many crystals desired, fast freezing entrapment of solutes, less than max concentration in the unfrozen phase </li></ul><ul><li>large crystals, slow freezing max concentration of solutes, tissue damage, partial dehydration, </li></ul><ul><li>local freeze concentration </li></ul><ul><li>freezer burn, sublimation of ice, dry brown spots on poultry, beef </li></ul><ul><li>antimicrobial effect due to concentration, intracellular freezing </li></ul><ul><li>destabilization of proteins, vitamin and pigment degradation, oxidation of lipids </li></ul>
  18. 18. Concentration and dehydration <ul><li>concentration > 20% moisture </li></ul><ul><li>dehydration < 20% moisture </li></ul><ul><li>evaporation, crystallization, sublimation, membrane separations </li></ul><ul><li>microorganisms survive, can recover, grow depending on a w </li></ul>
  19. 19. Controlled atmosphere <ul><li>control of atmosphere composition during storage </li></ul><ul><li>in packaging, gas impermeable films with absorbers </li></ul>
  20. 20. Modified atmosphere <ul><li>closed storage rooms, allow respiratory activity </li></ul><ul><li>in packaging, remove air, replace with other gases, N 2 , CO 2 </li></ul><ul><li>vacuum packaging </li></ul><ul><li>vacuum, nitrogen : cheese, meat </li></ul><ul><li>CO 2 : fruits and vegetables , meat </li></ul>
  21. 21. Ohmic heating <ul><li>short processing times < 90 s, then transfer into holding tube, aseptic packaging, commercial sterilization </li></ul><ul><li>no heat transfer surfaces, food heats inside, more efficient and uniform heating, reduces thermal quality defects </li></ul><ul><li>suitable for solid pieces containing liquid foods, like stews </li></ul>
  22. 22. Microwave heating <ul><li>rapid </li></ul><ul><li>can be use d in sterilization </li></ul><ul><li>applicable to packaged products </li></ul><ul><li>prevent contamination </li></ul><ul><li>thermal inactivation </li></ul>
  23. 23. High pressure processing <ul><li>better quality foods </li></ul><ul><li>ready-to-serve foods, vegetables </li></ul><ul><li>jams, preserves, meat, seafood </li></ul><ul><li>pulsed high pressure application </li></ul><ul><li>pressure environment, glycerol, edible oils, water/edible oil emulsions </li></ul><ul><li>700-900 MPa </li></ul>
  24. 24. Preservatives <ul><li>Legally allowed </li></ul><ul><li>1. toxicity </li></ul><ul><li>2. soluble in food </li></ul><ul><li>3. food pH </li></ul><ul><li>- inhibition of chemical/biochemical reactions </li></ul><ul><li>- antimicrobial effect </li></ul>
  25. 25. Organic acids <ul><li>acidity, antimicrobial effect </li></ul><ul><li>  </li></ul><ul><li>benzoic acid, Na- or Ca-benzoate </li></ul><ul><li>parabens (p-OH-methyl or propylbenzoate) </li></ul><ul><li>mold and yeast inhibitor </li></ul><ul><li>at low pH antibacterial, 0.1% </li></ul><ul><li>jams, preserves, bakery products, salad dressing </li></ul><ul><li>fruit juices </li></ul>
  26. 26. Organic acids <ul><li>sorbate (2,4-hexadienoic acid), K/Ca/Na salts </li></ul><ul><li>mold and yeast inhibitor </li></ul><ul><li>cheese, fruit juices, salads, bakery products </li></ul><ul><li>  </li></ul><ul><li>propionic acid, Ca/Na salts </li></ul><ul><li>rope inhibitors in bread, cheese, spreads </li></ul><ul><li>mold inhibitor at high pH </li></ul>
  27. 27. Organic acids <ul><li>acetic acid </li></ul><ul><li>rope inhibitor, mold inhibitor </li></ul><ul><li>bakery products  </li></ul><ul><li>lactic acid antimicrobial </li></ul><ul><li>citric acid acidulant </li></ul><ul><li>ion chelator </li></ul><ul><li>reduce oxidation </li></ul>
  28. 28. Nitrites and nitrates (NO 2 /NO 3 ) <ul><li>color stabilization </li></ul><ul><li>C. botulinum inhibitor </li></ul>
  29. 29. Sulfur compounds (SO 2 , HSO 3 - , SO 3 2- , S 2 O 5 2- ) <ul><li>antioxidant </li></ul><ul><li>browning inhibitor </li></ul><ul><li>antibacterial </li></ul><ul><li>limited use due to allergic reactions in some people </li></ul><ul><li>wines, dried fruits, vegetables </li></ul>
  30. 30. Salt (NaCl) <ul><li>control of water </li></ul><ul><li>antimicrobial </li></ul>
  31. 31. Antioxidants <ul><li>rancidity inhibitors </li></ul><ul><li>BHA, BHT, tocopherols </li></ul><ul><li>ascorbic acid </li></ul><ul><li>EDTA (ion chelator) </li></ul>
  32. 32. Smoke (phenols, formaldehyde, ketones, alcohols, acids) <ul><li>antioxidant </li></ul><ul><li>antibacterial, C. botulinum </li></ul>
  33. 33. Carbon dioxide <ul><li>antimicrobial </li></ul><ul><li>carbonated beverages </li></ul>
  34. 34. Antibiotics <ul><li>nisin </li></ul><ul><li>antibotulinal, antibacterial </li></ul><ul><li>processed cheese </li></ul><ul><li>natamycin </li></ul><ul><li>mold inhibitor </li></ul><ul><li>salami, cured cheese </li></ul>
  35. 35. Ethylene oxide <ul><li>antimicrobial </li></ul><ul><li>spices, nuts </li></ul><ul><li>aseptic packaging </li></ul>
  36. 36. Other antimicrobials <ul><li>chlorine (Na, Ca hypochlorite) </li></ul><ul><li>ozone </li></ul><ul><li>hydrogen peroxide </li></ul><ul><li> fresh fruits, vegetables </li></ul>
  37. 37. Packaging <ul><li>glass, metal, plastics, paper </li></ul><ul><li>transport of gases, water vapor, low MW components </li></ul><ul><li>resistance (mechanical, heat, chemical) </li></ul><ul><li>oxygen, carbon dioxide, moisture permeability </li></ul><ul><li>light transmission </li></ul><ul><li>inertness </li></ul>
  38. 38. Active packaging <ul><li>interact with food or package environment responding to changes </li></ul><ul><li>incorporation of different materials into the film or package headspace to improve package performance </li></ul><ul><li>- antimicrobial films </li></ul><ul><li>sulfur dioxide releaser </li></ul><ul><li>ethanol releaser </li></ul><ul><li>- oxygen scavengers </li></ul><ul><li>iron scavenger </li></ul><ul><li>photosensitive dye scavengers </li></ul><ul><li>enzyme scavengers </li></ul><ul><li>- moisture absorbers </li></ul><ul><li>dessicant packages, clay, minerals, silica </li></ul><ul><li>- ethylene absorbers </li></ul><ul><li>KMnO 4 </li></ul>
  39. 39. Smart packaging <ul><li>interact with food or package environment and give signals </li></ul><ul><li>indicate time/T history </li></ul><ul><li>indicate spoilage, remaining shelf life, end of shelf life </li></ul>
  40. 40. Aseptic packaging <ul><li>1. product sterilization </li></ul><ul><li>2. package sterilization </li></ul><ul><li>3. Aseptic filling and sealing </li></ul><ul><li>Longer shelf life, better quality (?) </li></ul>
  41. 41. Hurdle technology <ul><li>developed for limiting the growth of microorganisms in nonsterile foods (Leistner, 1978) </li></ul><ul><li>combined effects of preservation methods > sum of effects individually or large amounts of a single factor </li></ul>
  42. 42. Hurdle technology <ul><li>has been used unintentionally </li></ul><ul><li>pickles </li></ul><ul><li> pH + preservative (acid) + salt </li></ul><ul><li>sausage </li></ul><ul><li>a w + smoke + salt + spices + preservatives </li></ul><ul><li>IMF (dried fruit, soft cookies) </li></ul><ul><li>a w + heating + preservatives </li></ul><ul><li>past ı rma </li></ul><ul><li>salt + spices + a w </li></ul>
  43. 43. Hurdle technology <ul><li>Hurdles </li></ul><ul><li>T </li></ul><ul><li>pH </li></ul><ul><li>salt </li></ul><ul><li>redox potential </li></ul><ul><li>modified atmosphere </li></ul><ul><li>packaging </li></ul><ul><li>high pressure </li></ul><ul><li>radiation, other physical processes </li></ul><ul><li>competitive flora (lactic acid bacteria) </li></ul><ul><li>preservatives </li></ul>
  44. 44. all hurdles at the same intensity all hurdles at different intensity low initial microbial load good hygienic practice high initial microbial load low initial microbial load more nutrients substerilizing treatment damaged cells
  45. 45. <ul><li>t : chilling </li></ul><ul><li>F : heating </li></ul><ul><li>RVP : relative vapor pressure, aw </li></ul><ul><li>pH </li></ul><ul><li>Eh : redox potential </li></ul><ul><li>pres : chemical preservative </li></ul><ul><li>N : nutrients </li></ul>