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.

Improving fresh cheese shelf-life through hyperbaric storage at variable room temperature.

The changes in microbiological, physiochemical, and textural properties in fresh cheeses made from either cow or goat milk were observed under hyperbaric storage (HS, 50-100 MPa) at room temperature (RT) and compared with refrigerated storage under normal atmospheric pressure for 60 days. An initial microbial growth inhibition was observed for both cheese types, as well as a considerable inactivation of all endogenous microbiota under HS/RT (75-100 MPa/RT). This contributed to a higher stability of pH and color values, especially at the higher pressure at room temperature (100 MPa/RT) throughout 60 days storage. A compression effect occurred during HS/RT, resulting in higher whey loss, reduction in moisture content, and textural changes. Such changes tended to decrease over time, to values closer to the initial ones, with hardness values at the 60th day of storage at 75/RT similar to those observed for refrigeration on the 7th day and 1.4-fold higher than those observed at 100/RT. Overall, HS/RT reduced the microbial populations load during storage (≥5 log units in some cases), with minimal effects on most of the evaluated quality parameters. These results point to a considerable shelf-life extension of HS fresh cheeses, without temperature control, pinpointing HS as a more sustainable preservation strategy than refrigeration, with great potential for industrial application. PRACTICAL APPLICATION: The results presented in this study point to increased microbial stability of fresh cheeses when stored under hyperbaric storage without temperature control, leading possibly to an increased shelf-life, of up to 60 days. This kind of new food preservation strategy may be suitable for longer transportation of foods, where energy may not be handily and widely available, while additionally contributing to increased shelf-life and safety. Also, hyperbaric storage could be applied throughout the food storage, improving shelf-life with a lower carbon footprint than refrigeration.

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.

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.

Hyperbaric storage at variable room temperature - a new preservation methodology for minced meat compared to refrigeration.

Hyperbaric storage (HS) at variable room temperature (RT) has been proposed as an alternative to refrigeration at atmospheric pressure (RF/AP) for food preservation. Little information is available regarding the effect of HS in meat products. In this study the RT/HS effect was evaluated at 100 MPa and variable RT (≈20 °C) for minced meat preservation up to 24 h, initially for one batch. A further two different batches were studied independently. Microbiological and physicochemical parameters were analyzed to assess the feasibility of RT/HS, using storage at RF/AP and variable RT/AP (≈20 °C), for comparison. A post-hyperbaric storage (post-HS) was also tested over 4 days at RF/AP. For the first batch the results showed that RT/HS allowed a decrease of the total aerobic mesophile value (P < 0.05) when compared to the initial sample, whereas at RF/AP and RT/AP, values increased to > 6 Log CFU g-1 after 24 h. Similarly, Enterobacteriaceae increased > 1 and > 2 Log CFU g-1 at RF/AP and RT/AP, respectively, while yeasts and molds presented similar and lower overall loads compared to the initial samples for all storage conditions, whereas RT/HS always allowed lower counts to be obtained. Regarding pH, lipid oxidation, and color parameters, RT/HS did not cause significant changes when compared to RF/AP, except after 24 h, where pH increased. The three batches presented similar results, the differences observed being mainly due to the heterogeneity of the samples. RT/HS is a potential quasi-energetic costless alternative to RF for at least short-term preservation of minced meat. © 2018 Society of Chemical Industry.