Effects of High Hydrostatic Pressure on the Physical,Microbial, and Chemical Attributes of Oysters (Crassostrea virginica)

The change in the quality attributes (physical, microbial, and chemical) of oysters (Crassostrea virginica) after high hydrostatic pressure (HHP) treatment at 300 MPa at room temperature (RT, 25 °C) 300, 450, and 500 MPa at 0 °C for 2 min and control oysters without treatment were evaluated over 3 wk. The texture and tissue yield percentages of oysters HHP treated at 300 MPa, RT increased significantly (P < 0.05) compared to control. Aerobic and psychrotrophic bacteria in control oysters reached the spoilage point of 7 log CFU/g after 15 d. Coliform counts (log MPN/g) were low during storage with total and fecal coliforms less than 3.5 and 1.0. High pressure treated oysters at 500 MPa at 0 °C were significantly higher (P < 0.05) than oysters HHP treated at 300 MPa at 0 °C in lipid oxidation values. The highest pressure (500 MPa) treatment in this study, significantly (P < 0.05) decreased unsaturated fatty acid percentage compared to control. The glycogen content of control oysters at 3 wk was significantly higher (P < 0.05) when compared to HHP treated oysters [300 MPa, (RT); 450 MPa (0 °C); and 500 MPa (0 °C)]. HHP treatments of oysters were not significantly different in pH, percent salt extractable protein (SEP), and total lipid values compared to control. Based on our results, HHP prolongs the physical, microbial, and chemical quality of oysters.     

The influence of temperature,pH, and water immersion on the high hydrostatic pressure inactivation of GI.1 and GII.4 human noroviruses

Detection of human norovirus (HuNoV) usually relies on molecular biology techniques, such as qRT-PCR. Since histo-blood group antigens (HBGAs) are the functional receptors for HuNoV, HuNoV can bind to porcine gastric mucin (PGM), which contains HBGA-like antigens. In this study, PGM-conjugated magnetic beads were used to collect and quantify potentially infectious HuNoV strains GI.1 and GII.4 treated by high hydrostatic pressure (HHP). Both GI.1 and GII.4 strains used in this study showed increasing pressure sensitivity as judged by loss of PGM binding with decreasing temperature over a range of 1 to 35 °C. Both GI.1 and GII.4 were more resistant to pressure at pH 4 than at neutral pH. Because GI.1 was significantly more resistant to pressure than GII.4, it was used to evaluate HuNoV pressure inactivation in blueberries. GI.1 on dry blueberries was very resistant to pressure while immersion of blueberries in water during pressure treatments substantially enhanced the inactivation. For example, a 2 min-600 MPa treatment of dry blueberries at 1 and 21 °C resulted in < 1-log reductions while a 2.7-log reduction of GI.1 was achieved by a treatment at 500 MPa for 2 min at 1 °C when blueberries were immersed in water. In total, this novel study provides unique information for designing pressure processing parameters (pressure, temperature, and time) and product formulations (such as pH) to inactivate HuNoV in high-risk foods such as berries.     

High hydrostatic pressure treatment and storage of carrot and tomato juices: Antioxidant activity and microbial safety

The application of high hydrostatic pressure (HHP) (250 MPa, 35 °C for 15 min) and thermal treatment (80 °C for 1 min) reduced the microbial load of carrot and tomato juices to undetectable levels. Different combinations of HHP did not cause a significant change in the ascorbic acid content of either juice (P > 0.05). Both heat treatments (60 °C for 5–15 min and 80 °C for 1 min) resulted in a significant loss (P < 0.05) in the free‐radical scavenging activity as compared to untreated samples. HHP‐treated juices showed a small loss of antioxidants (below 10%) during storage. The ascorbic acid content of pressurized tomato and carrot juices remained over 70 and 45% after 30 days of storage, respectively. However, heat treatment caused a rapid decrease to 16–20%. Colour changes were minor (ΔE = 10) for pressurised juices but for heat‐pasteurised samples it was more intense and higher as a result of insufficient antioxidant activity. HHP treatment (250 MPa, 35 °C for 15 min) led to a better product with regard to anti‐radical scavenging capacity, ascorbic acid content and sensory properties (colour, pH) of the tomato and carrot juices compared to conventional pasteurisation. Therefore, HHP can be recommended not only for industrial production but also for safe storage of fresh juices, such as tomato and carrot, even at elevated storage temperatures (25 °C). Copyright © 2007 Society of Chemical Industry     

Microbial and Sensory Effects of Combined High Hydrostatic Pressure and Dense Phase Carbon Dioxide Process on Feijoa Puree

High hydrostatic pressure (HHP) is used for microbial inactivation in foods. Addition of carbon dioxide (CO₂) to HHP can improve microbial and enzyme inactivation. This study investigated microbial effects of combined HHP and CO₂ on Escherichia coli, Bacillus subtilis, and Saccharomyces cerevisiae, and evaluated sensory attributes of treated feijoa fruit puree (pH 3.2). Microorganisms in their growth media and feijoa puree were treated with HHP alone (HHP), or saturated with CO₂ at 1 atm (HHPcarb), or 0.4%w/w of CO₂ was injected into the package (HHPcarb+CO₂). Microbial samples were processed at 200 to 400 MPa, 25 °C, 2 to 6 min. Feijoa samples were processed at 600 MPa, 20 °C, 5 min, then served with and without added sucrose (10%w/w). Treated samples were analyzed for microbial viability and sensory evaluation. Addition of CO₂ enhanced microbial inactivation of HHP from 1.7‐log to 4.3‐log reduction in E. coli at 400 MPa, 4 min, and reduction of >6.5 logs in B. subtilis (vegetative cells) starting at 200 MPa, 2 min. For yeast, HHPcarb+CO₂ increased the inactivation of HHP from 4.7‐log to 6.2‐log reduction at 250 MPa, 4 min. The synergistic effect of CO₂ with HHP increased with increasing time and pressure. HHPcarb+CO₂ treatment did not alter the appearance and color, while affecting the texture and flavor of unsweetened feijoa samples. There were no differences in sensory attributes and preferences between HHPcarb+CO₂ and fresh sweetened products. Addition of CO₂ in HHP treatment can reduce process pressure and time, and better preserve product quality.     

Effect of different high pressure treatments on shucking,biochemical, physical and sensory characteristics of oysters to elaborate a traditional Taiwanese oyster omelette

BACKGROUND: Whole oysters (Crassostrea gigas) were processed using high‐pressure (HP) treatment (150–300 MPa) to determine their shucking and biochemical properties. Subsequently, HP‐treated oysters were cooked at 160 °C for 90 s, as when preparing the oyster omelette dish, to evaluate their physical and sensory characteristics as compared to raw oysters. RESULTS: The treatments of 250 and 300 MPa for 2 min and 0 min, respectively, resulted in 100% release. The pH of HP‐treated oysters increased slightly from 6.50 to 6.82, and the moisture contents of the HP‐treated oysters with or without further cooking were all higher than those of the control. The brightness, yellowness and cutting strength of HP‐treated oysters with further cooking changed insignificantly, while the redness decreased compared to the control. Sensory evaluation showed that oysters treated at 250 and 300 MPa oysters after cooking received higher quality scores than the control. CONCLUSIONS: HP processing at 250 and 300 MPa proved to be a good method for oyster shucking. The HP‐treated oysters cooked in the oyster omelette are acceptable to consumers. Overall, the application of HP as a processing method to improve the quality and acceptability of oysters and their related products would be possible. Copyright © 2009 Society of Chemical Industry     

Effect of combined treatments of ultrasound and high hydrostatic pressure processing on the physicochemical properties,microbial quality and shelf-life of cold brew tea

Effects of ultrasound combined with high hydrostatic pressure (HHP) on physicochemical properties,microorganisms and storage attributes of cold brew tea were investigated. HHP at 400 MPa/5 min/25 °C inactivated the total aerobic bacteria, yeast and mould in cold brewed tea prepared by static brewing (SB-tea) at 13 h/4 °C, ultrasonic bath (UB-tea) at 150 W/120 min/0 °C and ultrasonic pulveriser (UP-tea) at 600 W/40 min/0 °C, ensuring their microbiological safety. The results showed that there was no significant difference in the concentration of tea polyphenols between hot brewed tea prepared by 7 min/100 °C and cold brewed tea under different preparation conditions, while the caffeine in cold brewed tea was significantly lower (P < 0.05) than that in hot brewed tea. During the storage period of 8 days, compared with the untreated group, the cold brewed tea after HHP treatment had better microbiological safety. In addition, HHP treatment constantly maintained the tea polyphenols, pH, colour, antioxidant capacity and turbidity in cold brewed tea. The untreated and HHP-treated cold brew tea were evaluated by 20 trained volunteers. Results showed that UB-tea was more close to SB-tea than UP-tea in sensory profile, while HHP seem to maintain a good sensory profile as well. Therefore, this particular combined technology of ultrasonic bath and HHP displayed considerable potential for application in the cold brew tea manufacturing industry.     

Influence of packaging strategy on microbiological and biochemical changes in high‐pressure‐treated oysters (Crassostrea gigas)

BACKGROUND: High‐pressure (HP) treatment is being increasingly employed for commercial processing of oysters, but there is relatively limited information on the microbiological quality and enzymatic activity of HP‐treated in‐shell oysters. The objective of this research was to study the influence of packaging strategy on microbiological and biochemical changes in oysters HP treated at 260 MPa for 3 min or 400 MPa for 5 min at 20 °C and stored at 0 °C either aerobically on ice, in vacuum packaging (VP) or under modified atmosphere packaging (MAP; 40% CO₂, 60% N₂), compared with changes in untreated oysters. RESULTS: Both HP treatments reduced the microbiological load to below the detection limit (<100 colony‐forming units g^?1). MAP and VP also delayed subsequent microbial growth compared with aerobically stored samples. After 21 days of storage, total volatile base levels remained lower than the proposed acceptability limits for all samples; however, after 28 days, only oysters HP treated at 400 MPa, irrespective of the packaging system used, did not exceed this limit. HP increased the thiobarbituric acid‐reactive substance (TBARS) values of oysters, indicating increased lipid oxidation. During storage, TBARS values of all MAP and VP oysters remained lower than those of aerobically stored oysters. CONCLUSION: HP treatment, in combination with adequate chilled storage and MAP, can extend the shelf‐life and safety of oysters. Copyright © 2008 Society of Chemical Industry     

The effect of high hydrostatic pressure on the microbiological, chemical and sensory quality of fresh gilthead sea bream (Sparus aurata)

The effect of different temperature/time/pressure high hydrostatic pressure (HHP) treatment on quality and shelf life of sea bream were studied. Different high-pressure treatments (at 3, 7, 15 and 25 °C, 5–10 min and 220, 250 and 330 MPa) were tested to establish the best processing conditions for quality of sea bream. The effect of the process on the quality of the sample was examined by colour, trimethylamine nitrogen and thiobarbituric acid number analysis. Based on the results of the parameter, the best combinations of HHP treatments were determined as 3 °C/5 min/250 MPa–15 °C/5 min/250 MPa for sea bream. The effects of this combination treatment on sensory, chemical and microbiological properties of sea bream stored at 4 °C were studied. The results obtained from this study showed that the shelf life of untreated and HHP treated stored in refrigerator, as determined by overall acceptability of sensory and microbiological data, is 15 days for untreated sea bream and 18 days for treated sea bream at 3 °C/5 min/250 MPa and at 15 °C/5 min/250 MPa treated sea bream.     

Effects of high hydrostatic pressure on physicochemical and functional properties of walnut (Juglans regia L.) protein isolate

BACKGROUND: Walnut (Juglans regia L.) is a good source of protein that has potential application in new product formation and fortification. The main objectives of this study were to investigate the effects of high hydrostatic pressure (HHP) treatment (300–600 MPa 20 min) on physicochemical and functional properties of walnut protein isolate (WPI) using various analytical techniques at room temperature. RESULTS: The results showed significant modification of solubility, free sulfhydryl content and surface hydrophobicity with increased levels of HHP treatment, indicating partial denaturation and aggregation of proteins. Differential scanning calorimetry and fluorescence spectrum analyses demonstrated that HHP treatment resulted in gradual unfolding of protein structure. Emulsifying activity index was significantly (P < 0.05) increased after HHP treatment at 400 MPa, but significantly decreased (P < 0.05) relative to the untreated WPI with further increase in pressure. HHP treatment at 300–600 MPa significantly decreased emulsion stability index. Additionally, HHP‐treated walnut proteins showed better foaming properties and in vitro digestibility. CONCLUSION: These results suggest that HHP treatment could be applied to modify the properties of walnut proteins by appropriate of pressure levels, which will help in using walnut protein as a potential food ingredient. © 2012 Society of Chemical Industry     

Influence of high hydrostatic pressure processing on physicochemical characteristics of a fermented pomegranate (Punica granatum L.) beverage

The effect of high hydrostatic pressure at 500 MPa/10 min (HHP1), 550 MPa/10 min (HHP2) and 600 MPa/5 min (HHP3) on the microbiological, physicochemical, antioxidant and sensory characteristics of a fermented pomegranate (FP) beverage, stored for 42 days (4 ± 1 °C), was evaluated. The FP beverage was also pasteurized at 63 °C/30 min (VAT) and 72 °C/15 s (HTST). The high hydrostatic pressure (HHP) and VAT pasteurized beverages did not show microbial growth (<10 CFU/mL) throughout 42 days of storage. The physicochemical characteristics were not affected (p > 0.05) by HHP or pasteurization. Color of the samples showed significant differences (p ≤ 0.05) in all HHP processed and pasteurized beverages. Antioxidant activity, total phenolic compounds, flavonoids and anthocyanins increased slightly after HHP processing. Antioxidants decreased throughout the storage in all treatments. Both HHP processed and pasteurized beverages were well accepted by average consumers when evaluated using a 9-points hedonic scale.Industrial relevanceThe high hydrostatic pressure (HHP) improves the microbiological, antioxidant and sensorial stability of fermented pomegranate beverages during storage. The HHP is more common for processing fruit juices than for fermented beverages; therefore, it can be expanded to the fermented beverages industry, which could modify the today usual thermal processing methods and, or the addition of preservatives, that are not natural, for delivering high quality and healthier pomegranate fermented beverages to consumers.     

Quality Assessment of Commercially Processed Carbon Monoxide‐Treated Tilapia Fillets

Carbon monoxide (CO) has been used to stabilize the color of fish muscle during frozen storage and distribution. This study compared changes in the quality profiles of CO‐treated and untreated (UT) tilapia fillets stored at 21 to 22 °C (room temperature), 4 to 5 °C (refrigerated), and 0 °C (iced). Samples (n = 3) were analyzed at different time intervals for chemical, lipid oxidation, microbiological, color, and expert sensory profiles. CO samples contained greater (P < 0.05) apparent ammonia and total volatile base nitrogen (TVB‐N) at day 0, with greater (P < 0.05) TVB‐N throughout refrigerated and iced storage. At time 0, peroxide values (POV) and thiobarbituric‐acid‐reactive substances were lower (P < 0.05) for CO samples and continued to have lower trends throughout all storage temperatures. Microbiological analysis at time 0 did not show any differences between UT and CO samples. Redness (a*) color values were greater (P < 0.05) in CO tilapia at time 0; however, treated product showed a more rapid decline in a* throughout all storage temperatures. While expert sensory evaluation showed no statistical differences between UT and CO tilapia at time 0, CO product failed sensory assessment sooner than UT product when stored refrigerated and in ice.     

The Effects of Irradiation, High Hydrostatic Pressure, and Temperature during Pressurization on the Characteristics of Cooked-reheated Salmon and Catfish Fillets

ABSTRACT: Fully‐cooked salmon and catfish fillets were treated by ionizing radiation (0, 3, or 6 kGy), high hydrostatic pressure (HHP) (0, 414, or 690 MPa), 2 different temperatures during pressurization (ambient‐HHP approximately equal to 21 °C, or heated‐HHP = 70 °C), and combinations of the treatments. Kramer shear values increased for salmon and catfish fillets treated by HHP, heated‐HHP, and a combination treatment. Tenderness and juiciness scores of salmon and catfish fillets were lower with HHP, heated‐HHP, and a combination treatment. Irradiation decreased CIE a* values of salmon, and CIE b* values of salmon and catfish. Irradiation increased tenderness and juiciness scores of salmon and increased flavor intensity of catfish.     

A combined treatment of UV-assisted TiO2 photocatalysis and high hydrostatic pressure to inactivate internalized murine norovirus

Human norovirus (HuNoV) is a major cause of foodborne illness associated with shellfish consumption. A solidified agar matrix (SAM) was experimentally prepared using agar solution for inactivation of murine norovirus (MNV-1) as a surrogate for HuNoV in a simulation model approach. MNV-1 was injected inside the SAM for virus internalization, and the effects of single and combined UV-assisted TiO₂ photocatalysis (UVTP) and high hydrostatic pressure (HHP) treatments were determined. The internalized MNV-1 were reduced by 2.9-log₁₀ and 3.5-log₁₀, respectively, after single treatments of UVTP (4.5 mW/cm², 10 min) and HHP (500 MPa, 5 min, ambient temperature). However, the internalized MNV-1 was reduced by 5.5-log₁₀ (below the detection limit) when UVTP was followed by HHP, indicating a synergistic inactivation effect. Analysis of viral morphology, proteins, and genomic RNA allowed elucidation of mechanisms involved in the synergistic antiviral activity of combined treatments, which appeared to disrupt the MNV-1 structure and damage both the capsid protein and genomic RNA.Industrial relevanceHHP treatment of raw oysters has proved commercially successful, but there is a less evidence available regarding the potential of HHP for inactivation of localized viruses present inside foods. A sequential combination of UV-assisted TiO₂ photocatalysis (UVTP) and high hydrostatic pressure (HHP) achieved significantly higher inactivation of localized virus compared to individual treatments due to a synergistic mechanism. An experimentally prepared model food system was found useful to simulate foods with morphological variations and unpredictable viral internalization patterns. This UVTP-HHP combined treatment for inactivation of localized MNV-1 can be useful for disinfection of raw oysters and other similar foods.     

Effect of high hydrostatic pressure on the structure,physicochemical and functional properties of protein isolates from cumin (Cuminum cyminum) seeds

The effect of high hydrostatic pressure (HHP) treatment on the structure, physicochemical and functional properties of cumin protein isolate (CPI) was investigated. More aggregates, pores, irregular conformations and bigger particle size were observed for HHP-treated CPI. HHP resulted in an increase in α-helix, a decrease in β-strand and fluorescence intensity of CPI. Surface hydrophobicity (H_o) of CPI significantly increased after HHP treatment, from 343.35 for native CPI to 906.22 at 600 MPa (P < 0.05). HHP treatment at 200 MPa reduced zeta-potential and solubility of CPI, while had little effect at 400 and 600 MPa. Emulsifying activity and stability of CPI decreased after HHP treatment, of which droplet size of emulsions significantly increased (P < 0.05). HHP-treated CPI could form heat-induced gelation at lower temperature (68.5 °C) and improved storage modulus (G′) comparing to native one (80.6 °C), suggesting that CPI might be potential protein resources as gelation substitute in food system.     

Effect of Single‐ and Two‐Cycle High Hydrostatic Pressure Treatments on Water Properties,Physicochemical and Microbial Qualities of Minimally Processed Squids (Todarodes pacificus)

This study investigated the effect of single‐ and two‐cycle high hydrostatic pressure (HHP) treatments on water properties, physicochemical, and microbial qualities of squids (Todarodes pacificus) during 4 °C storage for up to 10 d. Single‐cycle treatments were applied at 200, 400, or 600 MPa for 20 min (S‐200, S‐400, and S‐600), and two‐cycle treatments consisted of two 10 min cycles at 200, 400, or 600 MPa, respectively (T‐200, T‐400, and T‐600). HHP‐treated samples had higher (P < 0.05) content of P_2b (immobilized water) and P₂₁ (myofibril water), but lower P₂₂ (free water) than those of control. The single‐ and two‐cycle HHP treatments at the same pressure level caused no significant difference in water state of squids. The two‐cycle HHP treatment was more effective in controlling total volatile basic nitrogen, pH, and total plate counts (TPC) of squids during storage, in which TPC of S‐600 and T‐600 was 2.9 and 1.8 log CFU/g at 10 d, respectively, compared with 7.5 log CFU/g in control. HHP treatments delayed browning discoloration of the squids during storage, and the higher pressure level and two‐cycle HHP were more effective. Water properties highly corresponded with color and texture indices of squids. This study demonstrated that the two‐cycle HHP treatment was more effective in controlling microbial growth and quality deterioration while having similar impact on the physicochemical and water properties of squids in comparison with the single‐cycle treatment, thus more desirable for extending shelf‐life of fresh squids.     

Differential Scanning Calorimetry Analysis of the Effects of Heat and Pressure on Protein Denaturation in Soy Flour Mixed with Various Types of Plasticizers

The effects of heat and pressure on protein denaturation in soy flour were explored by an experimental design that used pressure (atmospheric to 600 MPa), temperature (room to 90 °C), time (1 to 60 min), and type of aqueous plasticizer (NaCl, sucrose, betaine, and lactobionic acid (LBA)) as factors. When 50% (w/w) soy flour‐water paste was high hydrostatic pressure (HHP)‐treated for 20 min at 25 °C, the treatment at 200 MPa showed a small effect on denaturation of only the 7S soy globulin, but the treatment at 600 MPa showed a significant effect on denaturation of both the 7S and 11S soy globulins. The treatment at 60 °C showed a less‐pronounced effect on denaturation of the 11S globulin, even at 600 MPa, but that at 90 °C showed a similar extent of denaturation of the 11S globulin at 600 MPa to that at 25 °C. Chaotropic 2N NaCl, 50% sucrose‐, 50% betaine‐, or 50% LBA‐water solutions showed protective effects on protein denaturation during HHP treatment at 25 °C. Although LBA enhanced the extent of thermostability of soy protein less than did 2N NaCl, LBA exhibited better stabilization against pressure. The results from DSC analysis demonstrated that thermostable soy proteins were not always barostable.     

High Hydrostatic Pressure as a Hurdle for Zygosaccharomyces bailii Inactivation

The combined effects of high hydrostatic pressure (HHP, 172, 345, 517 or 689 MPa), duration of HHP treatment (0, 2, 4, or 10 min), water activity (a_w 0.98 or 0.95), and potassium sorbate (PS) concentration (0 or 1000 ppm) on Zygosaccharomyces bailii inactivation were evaluated at pH 3.5 and 21°C in laboratory model systems. Inactivation of the initial inoculum (? 1.0 times; 10⁵ CFU/mL) occurred when the pressure was 689 MPa regardless of a_w PS or duration of treatment. Lower pressure was required for Z. bailii inactivation in the presence of PS.     

Changes in K Value, Microbiological and Sensory Acceptability of High Pressure Processed Indian White Prawn (Fenneropenaeus indicus)

Indian white prawns headless and with shell on were vacuum packed in ethylene-vinyl alcohol pouches and subjected to high pressure treatment of 100, 270, 435 and 600 MPa at 25 °C for 5 min. Subsequently the treated samples were stored in ice (2?±?1 °C) along with control. The samples were periodically analysed to study the changes in total viable count, total Enterobacteriaceae count, K value and overall acceptability. Total viable count, total Enterobacteriaceae count and K value reduced proportionately with increasing high pressure treatment. However, K value and total viable count showed an increasing trend during chill storage whereas total Enterobacteriaceae decreased. No significant difference in K value was observed between control and 100 MPa, while higher pressure treated samples showed a significant difference (P?<?0.05). However, among the treatments 270 MPa was found to have better sensory acceptability.     

Inactivation of Escherichia coli and Listeria innocua in kiwifruit and pineapple juices by high hydrostatic pressure

Escherichia coli and Listeria innocua in kiwifruit and pineapple juices were exposed to high hydrostatic pressure (HHP) at 300 MPa for 5 min. Both bacteria showed equal resistance to HHP. Using low (0 degrees C) or sub-zero (-10 degrees C) temperatures instead of room temperature (20 degrees C) during pressurization did not change the effectiveness of HHP treatment on both bacteria in studied juices. Pulse pressure treatment (multiple pulses for a total holding time of 5 min at 300 MPa) instead of continuous (single pulse) treatment had no significant (p>0.05) effect on the microbial inactivation in kiwifruit juice; however, in pineapple juice pulse treatment, especially after 5 pulses, increased the inactivation significantly (p<0.05) for both bacteria. Following storage of pressure-treated (350 MPa, 20 degrees C for 60 s x 5 pulses) juices at 4, 20 and 37 degrees C up to 3 weeks, the level of microbial inactivation further increased and no injury recovery of the bacteria were detected. This work has shown that HHP treatment can be used to inactivate E. coli and L. innocua in kiwifruit and pineapple juices at lower pressure values at room temperature than the conditions used in commercial applications (>400 MPa). However, storage period and temperature should carefully be optimized to increase the safety of HHP treated fruit juices.     

Quality degradation kinetics of pasteurised and high pressure processed fresh Navel orange juice: Nutritional parameters and shelf life

A kinetic study of post processing quality loss was conducted after high pressure processing (600 MPa, 40 °C, 4 min) or thermal pasteurisation (80 °C, 60 s) of fresh Navel orange juice. Selection of processing conditions was mainly based on pectin methylesterase inactivation. Ascorbic acid loss, colour, viscosity and sensory characteristics were measured during storage at different isothermal conditions (0–30 °C). Increased shelf life (based on ascorbic acid retention) was achieved for high pressurised compared to thermally pasteurised juice, ranging from 49% (storage at 15 °C) to 112% (storage at 0 °C). Activation energy values for ascorbic acid loss were 68.5 and 53.1 kJ/mol, respectively, for high pressurised and thermally treated juice. High pressure processing resulted in better retention of flavour of untreated juice and superior sensory characteristics compared to thermal pasteurisation. Colour change was linearly correlated to ascorbic acid loss for both types of processing. Slightly higher apparent viscosity values were determined for high pressurised juice.Industrial relevanceApplication of high hydrostatic pressure on orange juice industry. Fresh orange juice is a product of high commercial and nutritional value due to its rich vitamin C content and its desired sensory characteristics. High Hydrostatic Pressure (HHP) is an alternative non-thermal technology that has been proposed for application on orange juice. Such a treatment denaturates enzymes and eliminates microorganisms responsible for spoilage of orange juice without detrimental effects on the sensory and nutritional quality of juice. The effect of HHP on the stability of fresh orange juice has been studied by different research groups, while orange juices processed with the new technology have already been commercially available in Japan, U.S.A., Mexico and Europe. However, a systematic kinetic approach of the effect of HHP on different quality indexes (not only microbial spoilage) immediately after processing, as well as during a long term storage of the processed orange juice is needed, in order to achieve an optimal process design and a successful application of the new technology in orange juice industry. Such kinetic data for parameters related to the quality and nutritional value of fresh orange juice were gathered in the present work providing therefore industry with useful information for the HHP stabilization of orange juice and the production of a high quality product. Due to the great benefits of HHP compared to the conventional pasteurization that emerged from this work regarding the quality, shelf life and nutritional characteristics of fresh orange juice, HHP technology is an advantageous alternative process for high valued products like orange juice.