Innovative Food Science and Emerging Technologies 13 (2012) 57–63                                                         ...
58                                  A. Vega-Gálvez et al. / Innovative Food Science and Emerging Technologies 13 (2012) 57...
A. Vega-Gálvez et al. / Innovative Food Science and Emerging Technologies 13 (2012) 57–63                           59et a...
60                                            A. Vega-Gálvez et al. / Innovative Food Science and Emerging Technologies 13...
A. Vega-Gálvez et al. / Innovative Food Science and Emerging Technologies 13 (2012) 57–63                                 ...
62                                               A. Vega-Gálvez et al. / Innovative Food Science and Emerging Technologies...
A. Vega-Gálvez et al. / Innovative Food Science and Emerging Technologies 13 (2012) 57–63                                 ...
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  1. 1. Innovative Food Science and Emerging Technologies 13 (2012) 57–63 Contents lists available at SciVerse ScienceDirect Innovative Food Science and Emerging Technologies j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / i f s e tApplication of high hydrostatic pressure to aloe vera (Aloe barbadensis Miller) gel:Microbial inactivation and evaluation of quality parametersAntonio Vega-Gálvez a, b,⁎, Claudia Giovagnoli a, Mario Pérez-Won a, Juan E. Reyes c,Judith Vergara a, Margarita Miranda a, Elsa Uribe a, Karina Di Scala d, ea Department of Food Engineering, Universidad de La Serena, Av. Raúl, Bitrán s/n, 599, La Serena, Chileb CEAZA, Center for Advanced Studies in Arid Zones, Universidad de La Serena, Av. Raúl Bitrán s/n, Box 599, La Serena, Chilec Department of Food Engineering, Universidad del Bio-Bío, Chillan, Chiled Food Engineering Research Group, Facultad de Ingeniería, Universidad Nacional de Mar del Plata, Av. Juan B. Justo 4302, Mar del Plata, Argentinae CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas), Argentinaa r t i c l e i n f o a b s t r a c tArticle history: High hydrostatic pressure (HHP) is an innovative technology which minimizes loss of physicochemical andReceived 5 April 2011 nutritional quality matching consumer demands for fresh-like foods. The aim of this study was to investigateAccepted 27 July 2011 the effect of high hydrostatic pressure (300, 400 and 500 MPa/1, 3 and 5 min) on microbial inactivation and quality parameters of A. vera gel after 60 days of storage. Shelf life was determined successfully by fittingEditor Proof Receive Date 7 September 2011 experimental microbial data to the modified Gompertz equation for samples treated at 300 MPa/1 min. TheKeywords: samples treated at 400 and 500 MPa during 1, 3 and 5 min presented undetectable levels of microorganismsHigh hydrostatic pressure counts. Based on microbiological results, the analysis of quality attributes was focused on the effects of HHPQuality indices (300, 400 and 500 MPa) during 5 min of processing. Antioxidant activity, which was analyzed by means ofMicrobial growth total polyphenols content and DPPH-radical scavenging activity, showed a maximum value at 500 MPa. AtShelf life 400 MPa, vitamin C showed the maximum retention (93%) and vitamin E increased the initial value of the gel.A. vera gel An increase of polysaccharides at 500 MPa also affected the gel firmness. Differences in surface color were also observed. Based on results, application of 500 MPa during 5 min may be successfully used to preserve main quality attributes of A. vera gel. Industrial relevance: The increasing demand for healthy foods with less physical damage and environmental friendly processing is giving new opportunities for the hurdle-technology concept of foods preservation. In this sense, high hydrostatic pressure presents an innovative technology to improve shelf life of A. vera gel leading to an enhancement of its quality attributes. © 2011 Elsevier Ltd. All rights reserved.1. Introduction the cell wall matrix (Femenia, García-Pascual, Simal, & Rossello, 2003). Some authors indicated that polysaccharides can exhibit Aloe vera (Aloe barbadensis Miller) which is a traditional medicinal pharmacological and physiological activities without help fromplant is used in food, pharmaceutical and cosmetic industries other components (Ramachandra & Srinivasa Rao, 2008). The(Miranda, Maureira, Rodríguez, & Vega-Gálvez, 2009). Its leaves are chemical composition of the gel also includes phytochemicals likeformed by a thick epidermis (skin) covered with cuticle surrounding polyphenolic compounds, tocopherols, flavonoids and ascorbic acidthe mesophyll, which can be differentiated into chlorenchyma cells with high antioxidant capacity which are able to reduce the freeand thinner walled cells forming the parenchyma (fillet). The radicals that cause oxidation reactions associated with biologicalparenchyma cells contain a transparent mucilaginous jelly, which is complications such as aging, cardiovascular disease, and carcinogen-referred to as aloe vera gel (Pisalkar, Jain, & Jain, 2011). Poly- esis (Miranda et al., 2009; Serrano et al., 2006; Vega, Uribe, Lemus, &saccharides account for most of the dry matter of the A. vera Miranda, 2007; Zheng & Wang, 2001).parenchyma, with two main types of polymers: acemannan, a storage Based on previous information about the gel, its use has increasedpolysaccharide rich in mannose units which is located within the due to its therapeutic and functional properties and hence itsprotoplast of the cells, and a wide variety of polysaccharides forming beneficial effects on humans (Miranda et al., 2009). Therefore, in order to extend its shelf life it becomes imperative to process it to ⁎ Corresponding author at: Department of Food Engineering, Universidad de La maintain almost all the bioactive chemical entities naturally presentSerena. Av. Raúl, Bitrán s/n, 599, La Serena, Chile. in the plant. In this sense, the application of an emerging processing E-mail address: (A. Vega-Gálvez). technique such as high hydrostatic pressure (HHP) can be utilized to1466-8564/$ – see front matter © 2011 Elsevier Ltd. All rights reserved.doi:10.1016/j.ifset.2011.07.013
  2. 2. 58 A. Vega-Gálvez et al. / Innovative Food Science and Emerging Technologies 13 (2012) 57–63replace, enhance or modify conventional techniques of food produc- spread on one DRBC plate. Plates were then incubated at 25 °C for 3–tion (Lewicki & Lenart, 2006; Rastogi, Angersbach, & Knorr, 2000; 5 days, and plates with 30–300 colonies were counted. MicrobialVega-Gálvez et al., 2011; Yucel, Alpas, & Bayindirli, 2010). In addition data were transformed into logarithms of the number of colony-to quality improvements and consumer benefits by gentle microbial forming units (log CFU/mL). Detection limit was 10 CFU/mLinactivation and improvement of mass transfer processes, HHP has according to WHO (1999).the potential to improve energy efficiency and sustainability of foodproduction (Donsí, Ferrari, & Maresca, 2010; Rastogi et al., 2000; 2.3.2. Microbial growth curve modelingToepfl, Mathys, Heinz, & Knorr, 2006). Moreover, changes in food Predictive microbiology is a useful tool to determine shelf life oftexture during HHP are strongly related to transformations in cell wall food products. The experimental data obtained were fitted to the re-polymers due to enzymatic and non-enzymatic reactions, being a parameterized version of the modified Gompertz equation accordingmajor challenge to use this novel technology to adjust raw materials, to the work of Briones, Reyes, Tabilo-Munizaga, and Pérez-Woningredients and processes to improve texture of processed plant based (2010).foods (Perera, Gamage, Wakeling, Gamlath, & Versteeg, 2010; Sila etal., 2008). & & ! λ−SL Therefore, the aim of this work was to study the effect of high log ðNðt ÞÞ = logðN max Þ−A⋅ exp − exp ðμ max ⋅2:7182Þ⋅ +1hydrostatic pressure on quality indices of A. vera gel including & & ! A λ−tantioxidant capacity, color, polysaccharides, vitamins C and E, poly- + A exp − exp ðμ max ⋅2:7182Þ +1 ð1Þ Aphenolics and texture as well as microbiological growth after 60 daysstorage. where N(t) is the viable cell concentration at time t. A is related to2. Materials and methods the difference decimal logarithm of maximum bacterial growth attained at the stationary phase and decimal logarithm of the2.1. Sample preparation and high hydrostatic pressure treatment initial value of cell concentration, μmax is the maximal specific growth rate, λ is the lag time, Nmax is the microbial threshold The whole fresh leaves of A. vera were provided by the INIA- value, SL is the microbiological acceptability limit (i.e., the time atIntihuasi, city of Coquimbo, Chile. Homogeneous leaves were selected which N(t) is equal to Nmax), and t is the storage time. The value ofaccording to size, color and freshness. Acibar (a yellow colored liquid) N max was set to 1 × 10 2 CFU/g for both mesophilic aerobicwas extracted by cutting the base of the leaves and allowing them to microorganisms and moulds and yeasts. This value is considereddrain vertically for 1 h. The epidermis was then separated from the as the upper acceptable limit for A. vera gel according to the Worldgel, which was extracted and homogenized by a Phillips Electric Health Organization (WHO, 1999).blender (HR1720, Amsterdam, The Netherlands). Samples of 25 mL The modified Gompertz equation was fitted to microbial datawere packaged into low density polyethylene bags. Then, they were using the nonlinear regression modulus of the GraphPad Prism v. 4.03placed in a cylindrical loading container at room temperature and (GraphPad Software, Inc., San Diego, CA, USA). The goodness of fit waspressurized at 300, 400 and 500 MPa during 1, 3 and 5 min for each evaluated using the coefficient of determination (R 2).treatment and compared to untreated A. vera gel (control). Water wasemployed as pressure-transmitting medium, working at 17 MPa/s 2.3.3. Determination of DPPH radical scavenging activityramp rate; decompression time was less than 5 s. A 2 L processing unit Free radical scavenging activity of the samples was determined(Avure Technologies Incorporated, Kent WA, USA) was used to using the 2,2-diphenyl-2-picrylhydrazyl (DPPH) method (Turkmen,pressurize the aloe samples. Then, they were removed and stored Sari, & Velioglu, 2005). Different dilutions of the extracts wereuntil further processing. prepared in triplicate. An aliquot of 2 mL of 0.15 mM DPPH radical in ethanol was added to a test tube with 1 mL of the sample extract. The2.2. Storage and sampling of processed juice reaction mixture was vortex-mixed for 30 s and left to stand at room temperature in the dark for 20 min. The absorbance was measured at Pressurized samples were stored at 4 °C. Quality and microbiolog- 517 nm, using a spectrophotometer (Spectronic® 20 Genesys™, IL,ical analyses were performed immediately after processing and at USA). 80% (v/v) ethanol was used to calibrate the spectrophotometer.intervals for up to 60 days storage. For all samples, three different Control sample was prepared without adding extract. All solvents andbatches were considered. reagents were purchased from Sigma (Sigma Chemical CO., St. Louis, MO, USA). Total antioxidant activity (TAA) was expressed as the2.3. Quality parameters percentage inhibition of the DPPH radical and was determined by Eq. (2):2.3.1. Microbiological analysis The samples were analyzed for numbers of mesophilic aerobic Abssamplemicroorganisms (MAM) and moulds and yeasts (MY). Twenty five % TAA = 1− × 100: ð2Þ AbscontrolmL or grams of each sample was obtained aseptically andhomogenized with a 225 mL peptone saline solution 0.1% (Difco,Detroit, USA) in a filter stomacher bag using a Stomacher®(Biocheck, S.A., Barcelona, Spain) at 240 rpm for 60 s. Further Where TAA is the total antioxidant activity and Abs is thedecimal dilutions were made with the same diluent, and duplicates absorbance. IC50, which is the concentration required to obtain aof at least three appropriate dilutions were plated on appropriate 50% antioxidant capacity, is typically employed to express themedia. In order to enumerate the mesophilic aerobic microorgan- antioxidant activity and to compare the antioxidant capacity ofisms, 1 mL of each dilution was pour-plated in Plate Count Agar various samples. IC50 was determined from a graph of antioxidant(PCA, Difco, Detroit, USA). After incubation at 30 °C for 72 h, plates capacity (%) against extract concentration (μg/mL sample).with 30–300 colonies were counted. To count the moulds andyeasts, 1 mL of the initial (10 − 1) dilution was spread on three plates 2.3.4. Determination of total polyphenolics (TPP)(0.3, 0.3 and 0.4 mL) of Dicloran Rose Bengal Chloramphenicol TPP were determined colorimetrically using the Folin-Ciocalteau(DRBC, Difco, Detroit, USA) agar, and 0.1 mL of each subsequent was reagent (FC) according to previous work with modifications (Chuah
  3. 3. A. Vega-Gálvez et al. / Innovative Food Science and Emerging Technologies 13 (2012) 57–63 59et al., 2008). 0.5 mL aliquot of the aloe gel extract solution was averaged. Total color difference (ΔE) was calculated using Eq. (3),transferred to a glass tube; 0.5 mL of reactive FC was added after 5 min where L0, a0 and b0 are the control values for fresh samples.with 2 mL of Na2CO3 solution (200 mg/mL) and shaken. The sample hÀ Á2 À Á2 À Á2 i0:5 aÃ−a0 + bÃ−b0 + LÃ−L0was then mixed on a vortex mixer and the reaction proceeded for ΔE = ð3Þ15 min at ambient temperature. Then, 10 mL of ultra-pure water wasadded and the formed precipitate was removed by centrifugationduring 5 min at 4000 ×g. Finally, the absorbance was measured in aspectrophotometer (Spectronic® 20 Genesys™, IL, USA) at 725 nm 2.4. Statistical analysisand compared to a gallic acid (GA) calibration curve. Results wereexpressed as mg GA/100 g dry matter. All reagents were purchased Two-way analysis of variance (ANOVA) (Statgraphics Plus® 5.1from Merck (Merck KGaA, Darmstadt, Germany). All measurements software, Statistical Graphics Corp., Herndon, USA) was used towere done in triplicate. indicate significant differences among samples. Significance testing was performed using Fishers least significant difference (LSD) test;2.3.5. Determination of vitamin C differences were taken as statistically significant when P b 0.05. The L-Ascorbic acid was determined by the 2,6 dichlorophenol- Multiple Range Test (MRT) included in the statistical program wasindophenol (Merck KGaA, Darmstadt, Germany) tritimetric meth- used to test the existence of homogeneous groups within each of theod according to AOAC method no. 967.21 (AOAC, 2000). A total of parameters analyzed.10 ± 0.1 g of triturated sample were weighed, filtered, and dilutedto a volume of 50 mL. All measurements were done in triplicate. 3. Results and discussionVitamin C content was expressed as mg vit C/100 g dry matter. 3.1. Effect of HHP on microbiological behavior: application of Gompertz2.3.6. Determination of vitamin E equation The vitamin E content was determined by means of theHPLC/fluorescence method described by Ubaldi, Delbono, Fusari, and The microbial load of the gel subjected to high hydrostaticServenti (2005). A liquid chromatograph (Shimadzu Instruments, Inc., pressure treatments (300, 400 and 500 MPa/1, 3 and 5 min) wasShimadzu LC-10 AD) was used for all determinations. α-Tocopherol investigated. The initial microbial load of fresh A. vera gel (control)was monitored with a fluorescence detector (Shimadzu Instruments, was 1.95 ± 0.048 and 2.37 ± 0.140 log CFU/mL for aerobic meso-Inc., Shimadzu RF-10 A xL). All measurements were done in triplicate. philic microorganisms (AMM) and yeasts (Y), respectively. MouldsVitamin E content was expressed as mg Vit. E/100 g d.m. were not detected. Fig. 1(A-B) showed the population change of both AMM and Y of samples treated at 300 MPa/1 min. The2.3.7. Determination of firmness untreated samples did not meet the microbiological requirements Firmness, which is the maximum force applied to puncture the according to WHO (WHO, World Health Organization, 1999)samples, was measured as an indicator of texture. Firmness of samples (AMM N2.0 log CFU/mL; Y N2.0 log CFU/mL). In the case of sampleswas measured using a Texture Analyzer (Texture Technologies Corp., treated at 300 MPa during 3 and 5 min, microbiological growthTA, XT2, Scardale, NY, USA). The puncture diameter was 2 mm, with a was observed at the end of the storage (60 days). In addition,travel distance of 20 mm and 1.7 mm s − 1 test speed. The maximum samples treated at 400 and 500 MPa during 1, 3 and 5 min hadforce was measured by making one puncture in each sample, using 10 undetectable levels of microorganisms on PCA (b10 CFU/mL).slabs per treatment. The mean value of maximum firmness for each These results were comparable with previous works of pressurizedtreatment was then calculated and the results were expressed as fruits juices (Buzrul, Hami, Largeteau, Demazeau, 2008;N/mm. Valdramidis et al., 2009). Yeasts are generally relatively sensitive to pressure, and HHP has been used successfully to extend the2.3.8. Determination of polysaccharides shelf life of acidic products whose spoilage microflora are Polysaccharides content was estimated by a colorimetric primarily yeasts, like fruit sauces, juices and purees (Patterson,analysis according to the methodology of Miranda et al. (2010). Linton, Doona, 2007). High-pressure inactivation is thought toOne gram of A. vera gel was extracted with 80 mL of water in bath be the result of a combination of morphological changes inat 100 °C for 2 h, with constant agitation and the samples were microbial cells, such as membrane perturbation and loss of itsvacuum-filtered. The filtrate was diluted to 100 mL in a beaker. function, compression of gas vacuoles, cell lengthening, formationTwo milliliters of the solution and 10 mL of absolute ethanol were of pores in the cell wall, and the destruction of ribosomesadded in plastic tubes; samples were centrifuged at 2500 × g for (Hartmann, Mathmann, Delgado, 2006; Lavinas, Miguel, Lopes,30 min, and the supernatant was removed; the precipitate was Valente Mesquit, 2008).dissolved in a final volume of 50 mL water. One milliliter of the When adjusting the experimental microbial data to the modifiedfiltered solution, 1 mL of phenol at 5 g/100 mL, and 5 mL of Gompertz equation, the following kinetic parameter estimations for theconcentrated sulphuric acid were added to the tops of the tubes. It maximum specific growth rate (μmax), lag-phase(λ) and the shelf lifewas allowed to settle for 30 min. Sample absorbance was (SL) for the aerobic mesophilic microorganisms and yeasts counts ofdetermined at 490 nm (Spectronic® 20 Genesys™, IL, USA). Total A. vera gel samples were obtained. For AMM: SL = 26.13 days,polysaccharide content was estimated by comparison with a μmax = 0.13 days− 1 and λ = 14.49 days; and for yeasts: SL = 26.19 days,standard curve generated from d-+-glucose analysis. All solvents μmax = 0.12 days− 1 and λ = 13.15 days. Therefore, for 300 MPa− 1 min,and reagents were purchased from Sigma (Sigma Chemical Co., St. the modified Gompertz equation was able to describe microbial AMMLouis, MO, USA). (R2 = 0.95) and Y growth (R2 = 0.95). The microbial shelf life estimated for pressure-treated 300 MPa/1 -2.3.9. Color measurement (ΔE) min A. vera gel stored at 4 °C was 26 days for both AMM and Y. In A. vera gel color was measured by a colorimeter (HunterLab, general, the tendency in pressure-treated products at higher pressureMiniScan™ XE Plus, Reston, VA, USA). Color was expressed in CIE L* and/or holding time treatments is to produce a significant increase in(whiteness or brightness), a* (redness/greenness) and b* (yellow- the lag phase times of mesophilic aerobic microorganisms. This mayness/blueness) coordinates, standard illuminant D65 and observer 10°. be due to a greater severity of cellular damage, as well as theFive replicate measurements were performed and results were increment of injured bacteria (Briones et al., 2010). As a food
  4. 4. 60 A. Vega-Gálvez et al. / Innovative Food Science and Emerging Technologies 13 (2012) 57–63 A DPPH Polyphenolics fresh Eq (1) treated 40 120.00 C IC50, Concentration Polyphenolics (mg 8 35 a 100.00 30 GA/ g d.m.) (ug mL-1) 25 80.00 7 20 60.00 c 6 15 bc 40.00 10 B b 20.00 5 5 A A Log UFC/mL 0 0.00 Untreated 300 400 500 4 Pressure (MPa) 3 Fig. 2. Effect of pressure (5 min) on DPPH-radical scavenging activity and total phenolics content of A. vera gel after 60 days storage at 4 °C. Values are mean ± standard deviation (n= 3). Identical letters above the bars indicate no significant difference (P b 0.05). 2 1 the samples treated at 300 and 500 MPa. Moreover, the highest antioxidant capacity, between pressurized samples was observed at 0 0 10 20 30 40 50 60 70 500 MPa. The effect of pressure on antioxidant capacity is not the same Storage time (days) among the food products. It has been reported that in tomato puree, DPPH was not changed by a HP treatment of 400 MPa/25 °C/15 min. B 9 However, during storage at 4 °C, total antioxidant capacity of pressur- ized (500 and 800 MPa/20 °C/5 min) orange juice was slightly de- 8 creased by approximately 15% after 21 days (Oey, Van der Plancken, Van Loey, Hendrickx, 2007). 7 Regarding TPC, they appeared to be sensible to the effect of processing. Levels of TPC of treated A. vera gel at 400 MPa (26.6 mg 6 GA/100 d.m.) decreased significantly (71%, P b 0.05) as compared to Log UFC/mL unprocessed samples (96.81 ± 14.76 mg GA/100 d.m.). TPC did not 5 present significant differences among pressurized samples (300– 4 500 MPa). Previously, the effect of HHP on TPC has been investigated with varied conclusions. Increase of TPC due to high hydrostatic 3 pressure was reported by other authors working with strawberry and blackberry purées (Patras, Brunton, Da Pieve, Butler, 2009); olives 2 (Tokuşoğlu, Alpas, Bozoğlu, 2009); apple puree (Landl, Abadias, Sárraga, Viñas, Picouet, 2010) and vegetables (McInerney, Seccafien, 1 Cynthia, Stewart, Bird, 2007). Others reported that total phenol content of fruit smoothies was fully degraded by day 30 of storage 0 0 10 20 30 40 50 60 70 suggesting that decrease in dissolved oxygen levels may limit total Storage time (days) degradation of this type of antioxidant (Keenan et al., 2010). Based on our results working at 500 MPa/5 min will lead into aFig. 1. Effect of pressure (300 MPa/1 min) on: A) aerobic mesophilic microorganisms product with high antioxidant capacity compared to the otherand B) yeasts of A. vera gel. Moulds were not detected. treatments. However, since effect of pressure on DPPH and TPC is not the same among the food products, further studies are needed topreservation method, the effectiveness of HHP in destroying micro- preserve the nutritional quality of different gels.organisms depends on a number of factors that must be taken intoaccount when optimizing pressure treatments for particular foods 3.3. Vitamin C and E content(Patterson et al., 2007). The factors are classified into three groups:process parameters, microbial characteristics and product parameters Fig. 3 shows the effect of process pressure on vitamin E and(Mañas Pagán, 2005). vitamin C after 60 days of storage. The initial contents of vitamin E and Based on previous microbiological results, the analysis of quality C were 0.21 mg/100 g d.m. and 127.59 mg/100 g d.m., respectively.attributes was focused on the effects of HHP (300, 400 and 500 MPA) Vitamin E acts as an antioxidant at the cell membrane level, protectingduring 5 min of processing. the fatty acids of the membranes against damage caused by free radicals (Repo-Carrasco, Espinoza, Jacobsen, 2003). Vitamin C is3.2. Effect on antioxidant capacity and total polyphenolics content very susceptible to oxidation under certain environmental conditions like heat, aw, presence of oxygen, heavy metal ions and alkaline pH The antioxidant capacity of the gel subjected to high pressure degrading their biological activity. Hence, vitamin C exhibitedtreatments (300, 400 and 500 MPa/5 min) was investigated based on significant degradation when subjected to HHP treatment in aDPPH-radical scavenging activity and total polyphenolics content. multivitamin system. This compound could be affected by chemicalFig. 2 presents the profiles of radical scavenging activity together with and enzymatic reactions occurring in food samples that may betotal polyphenolics content as function of process pressure (P b 0.05). enhanced by pressure (Valdramidis et al., 2009). In this investigationInitial contents of DPPH and TPC were 37392.95 ± 2822.05 μg/mL and vitamin C was affected by different pressurization treatments161.67 ± 49.14 mg GA/100 d.m., respectively. (P b 0.05). The retention of vitamin C after storage for 2 months at A significant decrease in antioxidant activity was noted in all 4 °C was 60% at 300 MPa, 93% at 400 MPa and 81% at 500 MPa. Oxygenpressurized gel samples compared to the control sample. The plays an important role in vitamin C degradation both at atmospherictreatment at 400 MPa showed the maximum reduction compared to pressure and at elevated pressure. Vitamin C pressure stability could
  5. 5. A. Vega-Gálvez et al. / Innovative Food Science and Emerging Technologies 13 (2012) 57–63 61 Vitamin E Vitamin C Polysacharides Firmness Polysacharides (mg/100 160 0.7 7000 10 B 9 Firmness (N/mm) A AC 6000 B 140 C 8 Vitamin C (mg/100 g d.m.) Vitamin E (mg/100 g d.m.) 0.6 A 5000 7 A g d.m.) 120 6 0.5 4000 d 5 100 B c 3000 a b 4 0.4 c 2000 3 80 a 2 b 0.3 1000 1 60 0 0 Untreated 300 400 500 0.2 40 Pressure (MPa) d 20 0.1 Fig. 4. Effect of pressure (5 min) on polysaccharides and firmness of A. vera gel after 60- 0 0.0 days storage at 4 °C. Values are mean ± standard deviation (n = 3). Identical letters untreated 300 400 500 above the bars indicate no significant difference (P b 0.05). Pressure (MPa)Fig. 3. Effect of pressure (5 min) on vitamin C and E of A. vera gel after 60 days storage at by-product of soybean (Mateos-Aparicio, Mateos-Peinado, Rupérez,4 °C. Values are mean ± standard deviation (n = 3). Identical letters above the bars 2011).indicate no significant difference (P b 0.05). Fig. 4 also shows the effects of pressure on A. vera gel firmness (Pb 0.05). Samples pressurized at 300 and 500 MPa showed the samebe explained by differences in molar ratio between ascorbic acid and final firmness of the samples. On the other hand, working at 400 MPathe initial oxygen content and possible existence of other anti or pro- showed similar firmness when compared to fresh samples. Firmness,oxidants (Oey, Van Loey, Hendrickx, 2008). which is a measure of the sample texture, can be related to modifications Evolution of vitamin C content in pressure treated food products in cell structure because of processing. Due to cell disruption, highhas been previously followed. Polydera, Stoforos, and Taoukis (2005) pressure processing facilitates the occurrence of enzymatic and non-reported 84% retention of vitamin C in orange juice after one month of enzymatic reactions. Substrates, ions and enzymes (PME) which arestorage of samples treated at 600 MPa/4 min. Patras et al. (2009) located in different compartments in the cells can be liberated andreported that levels of ascorbic acid in strawberry puree treated at 400 interact with each other during HHP treatment. The degree of celland 500 MPa were significantly lower than in fresh samples. disruption is not only dependent on the applied pressure level but alsoAscorbate retention of untreated and pressurized (400 MPa, 30 min, on the type of plant cell (Oey et al., 2008). In addition, textural changes20 °C) strawberry coulis decreases during storage at 4 °C. Initial during A. vera gel pressurization could be due to the enzymaticcontent was reduced to 29.38 mg/100 g (88.68%) after ultra-high demethylation of pectins, followed by the formation of calcium pectatehydrostatic pressure treatment. After 28 days of storage, it was complexes that diffuse to the cell wall/middle lamella facilitating26 mg/100 g (78.48%) for untreated strawberry coulis and interactions that lead to improved product texture already observed in22.8 mg/100 g (68.82%) for pressurized coulis (Sancho et al., 1999). pineapple juice (Perera et al., 2010); green beans (Krebbers, Matser,Barba et al. (in press) reported that pressurization at 400 and 600 MPa Koets, Van den Berg, 2002) and carrots (Trejo Araya et al., 2007). Thus,for 5–15 min preserved 92% of the ascorbic acid in the blueberry juice based on results, working at 500 MPa/5 min will produce a gel with highsamples. Other authors found no remarkable effects due to the polysaccharides content that cements the cells together resulting in antreatment on vitamin C content of carrots, tomatoes and broccoli after increase of the firmness sample (Adams, 2000).pressurization at 600 MPa (Butz et al., 2002). In literature, information about HHP effect on stability of fat 3.5. Effect on colorsoluble vitamins is less abundant than that on water soluble vitamins(Oey et al., 2007). From Fig. 3, it can be observed that 400 MPa/5 min For color “sensory” evaluation, ΔE is very important quantityimproved the content of vitamin E compared to the untreated sample. determining (Chen, 2008). Depending on the value of ΔE, the colorThis enhancement could be due to tocopherols scavenge lipid peroxy difference between the treated and untreated samples can beradicals and yield a tocopheroxyl radical that can be recycled back to estimated as not noticeable (0–0.5), slightly noticeable (0.5–1.5),the corresponding tocopherol by reacting with ascorbate or other noticeable (1.5–3.0), well visible (3.0–6.0) and great (6.0–12.0).antioxidants through different chemical reactions (Sattler, Gilliland, The effect of pressure on A. vera gel color after 60 days storageMagallanes-Lundback, Pollard, DellaPenna, 2004). In addition, reported the following ΔE values: 13.045 at 300 MPa, 23.3 at 400 MPadepending on the food matrix, a significant amount of vitamin E and 5.5 at 500 MPa (P b 0.05). From 300 to 400 MPa an increased oflinked to proteins or phospholipids could be released by processing. color is reported; however, when pressure is increased to 500 MPa, aThus, a higher content of this vitamin can be obtained compared to the notable reduction on ΔE is observed reaching values between 3 and 6non-processed sample (Casal, Amara, Oliveira, 2006). which according to Chen (2008) are appreciable differences. Further- more, the ΔE of the sample without pressure treatment showed a3.4. Effect on polysaccharides and firmness value of 9.105 ± 3.13 representing a large color difference according to Chen (2008). Some authors have reported that high pressure Polysaccharides account for most of the dry matter of the A. vera treatment (at low and moderate temperatures) has a limited effect onparenchyma (Femenia et al., 2003). A. vera gel presented an initial pigments (e.g. chlorophyll, carotenoids, anthocyanins, etc.) responsi-content of polysaccharides of 6155.96 ± 24.71 mg/100 g d.m. Fig. 4 ble for the color of fruits and vegetables. Nevertheless, the colorshows the effects of pressure on the polysaccharides of the sample compounds of high pressure processed fruits and vegetables can(P b 0.05). All treatments decreased the initial polysaccharides gel change during storage due to incomplete inactivation of enzymes andcontent. However, between pressurized samples, an increased in microorganisms, which can result in undesired chemical reactionsprocess pressure presented an increase in polysaccharides values. In (both enzymatic and non-enzymatic) in the food matrix (Barba et al.,fact, the treatment at 500 MPa presented the highest increase. These in press; Oey et al., 2008; Perera et al., 2010). These results indicateresults were in agreement with those reported by other authors that final color of gel samples is highly dependent on the operationworking with fruits (Yang, Jiang, Wang, Zhao, Sun, 2009) and with a pressure.
  6. 6. 62 A. Vega-Gálvez et al. / Innovative Food Science and Emerging Technologies 13 (2012) 57–634. Conclusions Lavinas, F. C., Miguel, M. A., Lopes, M. L., Valente Mesquit, Y. L. (2008). Effect of high hydrostatic pressure on cashew apple (Anacardium occidentale L.) juice preserva- tion. Journal of Food Science, 73(6), 273–277. Effects of high hydrostatic pressure treatments (300–500 MPa/1– Lewicki, P. P., Lenart, A. (2006). Osmotic dehydration of fruits and vegetables. : Taylor 5 min) on quality attributes as well as microbiological growth were Francis Group, LLC (Chapter 28). Mañas, P., Pagán, R. (2005). Microbial inactivation by new technologies of foodinvestigated in this work. Microbial data was successfully fitted to the preservation. Journal of Applied Microbiology, 98, 1387–1399.modified Gompertz equation. The highest antioxidant capacity Mateos-Aparicio, I., Mateos-Peinado, C., Rupérez, P. (2011). High hydrostaticincluding DPPH between pressurized samples was observed at pressure improves the functionality of dietary fibre in okara by-product from soybean. Innovative Food Science and Emerging Technologies, 11,500 MPa (P b 0.05). Pressurized samples presented similar values of 445–450.TPC (P b 0.05). All treatments decreased initial vitamin C content being McInerney, J. K., Seccafien, C. A., Cynthia, A. C., Stewart, M., Bird, A. R. (2007). Effects ofthe lowest values that at 300 MPa. Vitamin E showed a different trend, high pressure processing on antioxidant activity, and total carotenoid content and availability, in vegetables. Innovative Food Science and Emerging Technologies, 8,presenting an increased at 400 MPa/5 min. Among pressurized 543–548.samples, an increase in process pressure presented an increase in Miranda, M., Maureira, H., Rodríguez, K., Vega-Gálvez, A. (2009). Influence ofpolysaccharides values being the highest values those reported at temperature on the drying kinetics, physicochemical properties, and antioxidant500 MPa/5 min. Since polysaccharides contribute to food texture, HHP capacity of aloe vera (Aloe barbadensis Miller) gel. Journal of Food Engineering, 91, 297–304.also had significant effect on the firmness of the sample. Modifications Miranda, M., Vega-Gálvez, A., López, J., Parada, G., Sanders, M., Aranda, M., et al. (2010).in texture could be related to changes in cell structure because of Impact of air-drying temperature on nutritional properties, total phenolic contentprocessing (P b 0.05). Regarding to samples color, working at and antioxidant capacity of quinoa seeds (Chenopodium quinoa Willd.). Industrial Crops and Products, 32, 258–263.500 MPa/5 min presented the lower ΔE value (P b 0.05). Based on Oey, I., Van der Plancken, I., Van Loey, A., Hendrickx, M. (2007). Does high pressurethe mentioned results, working at 500 MPa/5 min could preserve the processing influence nutritional aspects of plant based food systems? Trends inmost relevant quality attributes of A. vera gel including microbiolog- Food Science Technology, 19, 300–308. Oey, I., Van Loey, L., Hendrickx, M. (2008). Texture changes of processed fruits andical, nutritional, antioxidant and physicochemical aspects. vegetables: Potential use of high-pressure processing. Trends in Food Science Technology, 19, 309–319. Patras, A., Brunton, N. P., Da Pieve, S., Butler, F. (2009). Impact of high pressure processing on total antioxidant activity, phenolic, ascorbic acid, anthocyaninAcknowledgments content and colour of strawberry and blackberry purées. Innovative Food Science and Emerging Technologies, 10, 308–313. The authors gratefully acknowledge the financial support for Patterson, M., Linton, M., Doona, C. (2007). Introduction to high pressure processing foods. In C. Doona, F. 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