Comparing Different Packaging Conditions on Quality Stability of High-Pressure Treated Serra da Estrela Cheeses during Cold Storage

Serra da Estrela cheese with a Protected Designation of Origin (PDO) is a traditional cheese that is wrapped in paper without vacuum. High-pressure processing (HPP), which requires vacuum packaging of the cheese, has been used for its cold pasteurization to overcome safety issues. In this study, two packaging systems were studied: non-vacuum greaseproof paper wrapping package and vacuum packaging in plastic film. Lactococci, lactobacilli, enterococci, and total mesophiles reached ca. 8 log cfu g^-1 and 4-6 log cfu g^-1 in control (unpasteurized) and HPP-treated cheeses, respectively, with no significant differences between packaging systems. Spoilage microorganisms' viable cell numbers were reduced to <3 log cfu g^-1 (quantification limit) in HPP-treated cheeses, independently of the packaging system. Yeasts and molds reached >5 log cfu g^-1 in non-vacuum paper-wrapped cheeses. A vacuum-packaging system enabled better control of cheese proteolysis, which was revealed to be closer to that of the original control cheese values at the end of the 10-month storage period. In addition, cheese stored under vacuum film packaging became harder than non-vacuum paper-wrapped cheeses at each time point. Overall, conventional non-vacuum paper wrapping is adequate for short storage periods (<3 months), but for long periods vacuum packaging in plastic film is preferable.

Effect of high pressure pre-treatment on raw ewes' milk and on subsequently produced cheese throughout ripening

BACKGROUND

Raw ewe's milk, as used to manufacture Serra da Estrela Protected Designation of Origin cheese, was pre-treated by high pressure processing (HPP), using previously optimized conditions (121 MPa for 30 min), aiming to evaluate its effect on milk technological properties for subsequent cheese production, namely the impact on resulting curd, whey and cheese throughout ripening.

RESULTS

The cheese yield increased 10.4% as a result of milk pre-treated by HPP, which also yielded inactivation of beneficial microbial groups. After 60 days of ripening, both treated and control cheeses showed no significant differences (P ≥ 0.05) with respect to quantified microbial load or basic physicochemical quality parameters.

CONCLUSION

HPP appears to be a promising non-thermal treatment for ewes' milk to inactivate contaminant bacteria but with no negative effect on lactic acid bacteria, which is very important for the unique characteristics of Serra da Estrela cheese. © 2020 Society of Chemical Industry.

Effects of high-pressure processing on fungi spores: Factors affecting spore germination and inactivation and impact on ultrastructure

Food contamination with heat-resistant fungi (HRF), and their spores, is a major issue among fruit processors, being frequently found in fruit juices and concentrates, among other products, leading to considerable economic losses and food safety issues. Several strategies were developed to minimize the contamination with HRF, with improvements from harvesting to the final product, including sanitizers and new processing techniques. Considering consumers' demands for minimally processed, fresh-like food products, nonthermal food-processing technologies, such as high-pressure processing (HPP), among others, are emerging as alternatives to the conventional thermal processing techniques. As no heat is applied to foods, vitamins, proteins, aromas, and taste are better kept when compared to thermal processes. Nevertheless, HPP is only able to destroy pathogenic and spoilage vegetative microorganisms to levels of pertinence for food safety, while bacterial spores remain. Regarding HRF spores (both ascospores and conidiospores), these seem to be more pressure-sensible than bacterial spores, despite a few cases, such as the ascospores of Byssochlamys spp., Neosartorya spp., and Talaromyces spp. that are resistant to high pressures and high temperatures, requiring the combination of both variables to be inactivated. This review aims to cover the literature available concerning the effects of HPP at room-like temperatures, and its combination with high temperatures, and high-pressure cycling, to inactivate fungi spores, including the main factors affecting spores' resistance to high-pressure, such as pH, water activity, nutritional composition of the food matrix and ascospore age, as well as the changes in the spore ultrastructure, and the parameters to consider regarding their inactivation by HPP.

Effect of high-pressure processing on carotenoids profile, colour, microbial and enzymatic stability of cloudy carrot juice

The objective of this work was to assess the impact of high-pressure processing (HPP) on the carotenoid profile, colour as well as the microbial and enzymatic stability of cloudy carrot juice. The predominant carotenoids in the fresh juices were by far the provitamin A carotenoids β-carotene and α-carotene. Others were ζ-carotene, phytofluene, phytoene and lutein. HPP at 300 MPa in three cycles caused the highest carotenoids degradation (41%) whereas the lowest degradation (26%) was achieved at 600 MPa. The highest inactivation of POD (31%) and PPO (57%) was achieved with 600 MPa and 300 MPa applied in three cycles, respectively what indicates that POD is more responsible for carotenoids degradation. The colour differences (ΔE^*_ab) between fresh juice and HPP-treated juices ranged from 3.02 to 4.15 CIELAB units. As far as the impact on microorganism was concerned, there was a clear trend between the applied pressure and the microbial reduction achieved.

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.

Landmarks in the historical development of twenty first century food processing technologies

Over a course of centuries, various food processing technologies have been explored and implemented to provide safe, fresher-tasting and nutritive food products. Among these technologies, application of emerging food processes (e.g., cold plasma, pressurized fluids, pulsed electric fields, ohmic heating, radiofrequency electric fields, ultrasonics and megasonics, high hydrostatic pressure, high pressure homogenization, hyperbaric storage, and negative pressure cavitation extraction) have attracted much attention in the past decades. This is because, compared to their conventional counterparts, novel food processes allow a significant reduction in the overall processing times with savings in energy consumption, while ensuring food safety, and ample benefits for the industry. Noteworthily, industry and university teams have made extensive efforts for the development of novel technologies, with sound scientific knowledge of their effects on different food materials. The main objective of this review is to provide a historical account of the extensive efforts and inventions in the field of emerging food processing technologies since their inception to present day.