Impact of different hyperbaric storage conditions on microbial, physicochemical and enzymatic parameters of watermelon juice

High Pressure and Pasteurization Effects on Dairy Cream

Dairy cream, a common ingredient in various dishes and food products, is susceptible to rapid microbial growth due to its high water activity (≈0.97) and pH (≈6.7). Thus, it requires proper processing conditions to ensure food safety and extend shelf life. High-pressure processing (HPP) has emerged as a nonthermal food pasteurization method, offering an alternative to conventional heat-based techniques to obtain tastier, fresh-like, and safe dairy products without undesirable heat-induced alterations. This study assessed the impact of HPP (450 and 600 MPa for 5 and 15 min at 7 °C) and thermal pasteurization (75 °C for 15 s) on the microbiological and physicochemical attributes of dairy cream immediately after processing and throughout refrigerated storage (4 °C). HPP-treated samples remained microbiologically acceptable even on the 51st day of storage, unlike thermally pasteurized samples. Moreover, HPP decreased inoculated Escherichia coli and Listeria innocua counts by more than 6 log units to undetectable levels (1.00 log CFU/mL). pH, color (maximum variation of ΔE* up to 8.43), and fatty acid profiles remained relatively stable under varying processing conditions and during storage. However, viscosity exhibited higher values for HPP-treated samples (0.028 ± 0.003 Pa·s) compared to thermally processed ones (0.016 ± 0.002 Pa·s) by the 28th day of storage. Furthermore, volatile compounds (VOCs) of all treated samples presented a tendency to increase throughout storage, particularly acids and aliphatic hydrocarbons. These findings show HPP's potential to significantly extend the shelf life of highly perishable dairy cream by at least 15 days compared to thermal pasteurization.

Impact of Fermentation and Pasteurization on the Physico-Chemical and Phytochemical Composition of Opuntia ficus-indica Juices

Opuntia ficus-indica fruits are a source of valuable compounds, presenting a high nutritional value and several health benefits. However, due to its low shelf life and increased production, there are considerable post-harvest losses of this cactus fruit. So, ways need to be found to drain the increased production of this fruit that is being wasted. The chemical composition of prickly pear makes it an appealing substrate for fermentation. This study investigates the production of fermented beverages produced from Opuntia ficus-indica cv 'Rossa' and evaluates the effects of different fermentation times (18 and 42 h) and post-fermentation pasteurization by high-pressure (500 MPa for 10 min) and temperature (71.1 °C for 30 s) on the physico-chemical and biological characteristics of the produced beverages. According to the results, the beverage produced from 48 h of fermentation has an alcohol content value of 4.90 ± 0.08% (v/v) and a pH of 3.91 ± 0.03. These values contribute to an extended shelf life and improved organoleptic characteristics compared to the sample fermented for 18 h. Additionally, the longer fermentation resulted in 50% fewer total soluble solids, 90% less turbidity, and lower pH when compared to the sample fermented for 18 h. Moreover, overall, high-pressure processing demonstrates better retention of "fresh-like" characteristics, along with higher levels of phytochemical compounds and antioxidant capacity, similar to those observed in the juice for SO^•- and NO^•-scavenging abilities.

Effect of High-Pressure and Thermal Pasteurization on Microbial and Physico-Chemical Properties of Opuntia ficus-indica Juices

Opuntia fruits are recognized for their richness in nutrients and in bioactive compounds, being also highly appreciated by consumers as a juice. Nevertheless, without further processing, prickly pear juices have a short shelf-life, hampering their commercial use. In this work, thermal (TP) and high-pressure (HPP) pasteurization were applied to juices from Opuntia ficus-indica cultivars ‘Rossa’, ‘Gialla’, and ‘Bianca’ to understand the impact of those methods on the microbial safety, physico-chemical properties, and the nutritional content of the samples, over storage at 4 °C. In general, thermal pasteurization at 71.1 °C for 30 s increased the shelf-life by 22 days, and high-pressure pasteurization at 500 MPa for 10 min increased the shelf-life by 52 days with regard to microbial growth as well as maintenance of physical-chemical characteristics. The application of these two pasteurization methods delayed changes in the physico-chemical characteristics of the juices, with a more pronounced effect on the titratable acidity, °Brix and browning. For the same periods of time, the application of pasteurization methods decreased the variation in these quality parameters by around 75%. Similarly, these methods were shown to have the same effect on the polyphenolic concentration as well as the antioxidant activity of the juices. In particular, HPP was more efficient in preventing a decrease in °Brix and increase in titratable acidity, which normally negatively affect the flavor of the juices.

Vacuum Concentration Improves the Quality and Antioxidant Capacity of Pear Paste

A vacuum concentration method was established to produce pear paste using fresh pear juice in this study. The optimal condition was determined by comparing the quality indexes, contents of total phenol and flavonoid, and antioxidant properties of the pear paste produced by traditional heating concentration and vacuum concentration. Electronic nose and electronic tongue were introduced in this study to provide digital smell and taste indicators. The results showed that the best vacuum concentration temperature was 65°C, which led to the best sensory evaluation score and pear paste quality. The browning degree and soluble quinones were the lowest in all tested temperatures, and the content were 60.12% and 72.88% compared with the heating method, respectively. While the values were 148.29%, 209.44%, 310.86%, 120.37%, 106.24%, and 181.26% of total phenol, total flavonoid, vitamin C, 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) and hydroxyl (·OH) radical scavenging rates, and total reducing power, respectively. The electronic nose could effectively distinguish the vacuum-concentrated pear paste from the traditional heating-concentration pear paste and could provide quality guidance on their flavor differences through characteristic sensors. The electronic tongue tests showed that the vacuum-concentrated pear paste had larger freshness and richness kurtosis. The pear paste made by the optimized vacuum concentration method had higher retention of nutritional and functional components and higher antioxidant capacity, which could be clearly differentiated from the traditional process, thus this method had an applicable potential.

Preservation of high pressure pasteurised milk by hyperbaric storage at room temperature versus refrigeration on inoculated microorganisms, fatty acids, volatile compounds and lipid oxidation

High pressure pasteurised (HPP) milk was stored by hyperbaric storage at room temperature (HS/RT) (50-100 MPa at 20 °C) and compared with refrigeration (RF), to assess the effect on two pathogens surrogates and a pathogenic, up to 120 days, and on fatty acids, volatile organic compounds (VOCs) and secondary lipid oxidation over 60 days. HS/RT (75-100 MPa) was able to inactivate at least 6.68/6.31/6.03 log CFU/mL of Escherichia coli/Listeria innocua/Salmonella Senftenberg (to below the detection limit), while RF resulted only in minor changes. Overall, fatty acids profile remained stable under HS/RT, although secondary lipid oxidation showed slightly higher values. In addition, both HS/RT and RF showed stable and similar VOCs profiles and off-flavour indicative compounds were not detected, except for the lowest pressure (50 MPa) after 40 days. HS/RT preserved HPP milk with enhanced microbial safety, shelf-life and quality compared to RF, being in addition quasi-energetically costless and more sustainable than RF.

Nutritional, Physicochemical, and Endogenous Enzyme Assessment of Raw Milk Preserved under Hyperbaric Storage at Variable Room Temperature

Raw milk (a highly perishable food) was preserved at variable room temperature (RT) under hyperbaric storage (HS) (50-100 MPa) for 60 days and compared with refrigeration (RF) under atmospheric pressure (AP) on quality, nutritional, and endogenous enzyme activity parameters. Overall, a comparable raw milk preservation outcome was observed between storage under AP/RF and 50/RT after 14 days, with similar variations in the parameters studied indicating milk degradation. Differently, even after 60 days (the maximum period studied) under 75-100/RT, a slower milk degradation was achieved, keeping most of the parameters similar to those of milk prior to storage, including pH, titratable acidity, total solid content, density, color, viscosity, and volatile organic and fatty acid profiles, but with higher free amino acid content, signs of an overall better preservation. These results indicate an improved preservation and enhanced shelf life of raw milk by HS/RT versus RF, showing HS potential for milk and highly perishable food preservation in general.

Is overnight fresh juice drinkable? The shelf life prediction of non-industrial fresh watermelon juice based on the nutritional quality, microbial safety quality, and sensory quality

OBJECTIVE

The aim of this study was to obtain the time range of non-industrial fresh watermelon juice (FWJ), which is widely used in the catering industry under different storage conditions, with safe-drinkable quality, and the drinking time range of fresh juice with good nutritional quality and sensory quality.

METHOD

The quality of non-industrial FWJ was audited by assessing the shelf life of non-industrial FWJ through microbial safety, nutritional, and sensory quality investigating during 24 h of storage at 4, 25, and 37°C.

RESULTS

According to the microbial safety quality, the safe drinking time of FWJ was within 12, 4, and 4 h when stored at 4, 25, and 37°C, respectively. Based on the nutritional and sensory quality, FWJ was drinking with good quality within 2 h, and with just acceptable quality for no more than 4 h when stored at 4 or 25°C. Electronic nose and gas chromatography-mass spectrometry (GC-MS) could effectively distinguish and identify the changes in volatile components in FWJ under different storage conditions.

CONCLUSION

It is a feasible method to predict the shelf life of non-industrial FWJ by this method, and hence to guarantee non-industrial FWJ being drinking with safety and health, and it might be used in many other fresh juice shelf life predictions.

Hyperbaric storage at room like temperatures as a possible alternative to refrigeration: evolution and recent advances

From 2012, the preservation of food products under pressure has been increasingly studied and the knowledge acquired has enlarged since several food products have been studied at different storage conditions. This new food preservation methodology concept called Hyperbaric Storage (HS) has gain relevance due to its potential as a replacement or an improvement to the conventional cold storage processes, such as the traditional refrigeration (RF), or even frosting, from the energetic savings to the reduction of the carbon foot-print. Briefly, HS is capable to inhibit the microbial proliferation or its inactivation which results in the extension of the shelf-life of several food products when compared to RF. Moreover, the overall quality parameters seem not to be affected by HS, being the differences detected on samples over storage similar to lower when compared to the ones stored at RF. This review paper aims to gather data from all studies carried out so far regarding HS performance, mainly at room temperature on fruit juices, meat and fisheries, as well on dairy products and ready-to-eat meals. The HS advantages as a new food preservation methodology are presented and explained, being also discussed the industrial viability and environmental impact of this methodology, as well its limitations.

Effects of Chemical and Natural Additives on Cucumber Juice's Quality, Shelf Life, and Safety

Microbial contamination affects beverages' lifetime, quality, and safety. Cucumber crops are seasonally spoiled because of the overproduction. The current study aimed to maximize the importance of natural preservatives and reduce the usage of artificial ones to prolong the cucumber juice's storage life, enhance flavor, and control the microorganisms after protein isolate and organic acids supplementation. The additions included control (no addition), citric, benzoic acid, sodium salts, kidney bean pepsin hydrolysate (KPH), chicken egg protein isolate (CEPI), duck egg protein isolate (DEPI), and quail egg protein isolate (QEPI) as J-Control, J-Citric, J-Benzoic, J-sod. Citrate, J-sod. Benzoate, J-KPH, J-CEPI, J-DEPI, and J-QEPI, respectively. The antioxidant activity of these additives and juices was evaluated by DPPH radical scavenging activity. The antimicrobial activity, including antibacterial and antifungal activities, was evaluated by using disc assay and the radial growth of fungal mycelium, respectively. The phenolic compounds and flavonoids were estimated by a spectrophotometer as Gallic acid equivalent (GAE) and quercetin equivalent (QE), respectively. Moreover, chemical parameters such as pH, total soluble solids (TSS), Titratable acidity (TTA), and Vitamin C were evaluated by AOAC. Finally, the color properties were estimated by a spectrophotometer, using the Hunter method. KPH had higher significant (p ≤ 0.05) antioxidant activity (88%), along with antimicrobial activity. It significantly (p ≤ 0.05) reduced the growth of G+ and G- bacteria by 71%-97% and 58%-66% respectively. Furthermore, it significantly (p ≤ 0.05) inhibited the tested fungi growth by 70%-88% and the other additives less than that. During the storage of cucumber juice for an interval of zero, two, four, and six months, the phenolic compounds and flavonoids were significantly (p ≤ 0.05) decreased. Consequently, the potential activity of the juice was reduced; in addition, pH and vitamin C were significantly (p ≤ 0.05) decreased during the storage period. Meanwhile, the TSS and Titratable acidity were significantly raised. As for color and sensory properties, J-sod. Benzoate, J-KPH, J-CEPI, and J-DEPI had significantly (p ≤ 0.05) high scores in color, taste, and flavor against the control. Generally, the usage of natural additives extends the cucumber juice's lifetime and increased the manufacture of high-quality and valuable juice.

Improvement of the refrigerated preservation technology by hyperbaric storage for raw fresh meat

BACKGROUND

This work aimed to compare raw fresh meat (minced bovine and pork in pieces) preserved by hyperbaric storage (HS) at room-like temperature (75 MPa/25 °C) and HS at cold temperatures (60 MPa/10 °C) for up to 60 days, being both compared to refrigeration (RF, 4 °C).

RESULTS

HS conditions showed microbial load reductions over 60 days of storage, leading to a possible shelf-life extension when compared to samples at RF. Moreover, between both HS conditions similar results were found at the 60^th day, reaching in some cases values < 1.00 log CFU g^-1 . Overall, pH presented an increase with storage for both HS conditions (e.g. over 30 days, from 5.51 ± 0.02 to 5.70 ± 0.01 and 5.85 ± 0.03, for 60 MPa/10 °C and 75 MPa/25 °C, respectively, on pork meat in pieces, PP) contrary to RF where pH values decreased (from 5.51 ± 0.02 to 5.33 ± 0.03). Regarding moisture content and drip loss, lower and higher values were found, respectively at 75 MPa/25 °C, mainly in bovine minced meat. Overall, colour ΔE* did not present considerable differences for both samples under all storage conditions. Lipid oxidation presented an increase tendency over time, with both HS conditions showing the higher values (1.795 ± 0.217 and 2.169 ± 0.117 for 60 MPa/10 °C and 75 MPa/25 °C, respectively, compared to 0.895 ± 0.084 μg MDA g^-1 in PP samples at the 30^th day).

CONCLUSION

Although several advantages were found further studies should be carried out in order to optimize the HS conditions for raw fresh meat and assess the impact of this preservation methodology on other meat quality parameters as for instance sensorial aspects. © 2019 Society of Chemical Industry.

Hyperbaric Storage at Room Temperature for Fruit Juice Preservation

Hyperbaric storage is an innovative preservation method that consists of storing food under pressure, either at room or at low temperature, for time periods of days, weeks, or months. Recent scientific literature shows that hyperbaric storage at room temperature (HS-RT) could be an efficient method for fruit juice preservation. Depending on the level applied, pressure can inhibit and even inactivate the endogenous microflora of the fresh juice, while properly preserving other organoleptic and quality indicators. Even though the method has not yet been implemented in the food industry, its industrial viability has been evaluated from different points of view (product quality, consumer acceptation, vessel design, economic, or environmental, among others). The results reveal that HS-RT is effective in extending the shelf-life of both acidic and low-acidic fruit juices. Moreover, the energetic costs and the carbon footprint of HS-RT are considerably lower than those of refrigeration, therefore, HS-RT could be a reliable and environmentally friendly alternative to conventional cold storage. However, before industrial implementation, much more research is needed to clarify the effects of the storage conditions on the agents that cause fruit juice deterioration.

Influence of multiple environmental factors on the quality and flavor of watermelon juice

Environmental factors (heat, pH, oxygen, light) can induce significant quality changes in watermelon juice during processing. To ascertain the effect of such factors on the quality of watermelon juice, the total soluble solids (TSSs), turbidity, lycopene content, color, and flavor were evaluated during different treatments. The pH had a slight impact on the content of lycopene, but had an obvious impact on turbidity. Heat, oxygen, and illumination had considerable effects on the color of watermelon juice, and the results were visible. The content of aldehydes [hexanal, nonanal, (E)-2-noneal, (Z)-6-nonenal] and ketones (6-methyl-5-hepten-2-one, geranylacetone, β-ionone) decreased in treated watermelon juices, while those of 1-nonanol, (Z)-3-nonen-1-ol and (E,Z)-3,6-nonadien-ol increased during illumination. The order of influence of environmental factors on watermelon-juice quality was light > pH > oxygen > heat.