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Consumers' desire for healthy and safe foods makes it necessary to explore the possibilities of using natural antioxidants. A number of herbs and spices have been found to show a strong inhibitory effect on oxidation processes in meat and meat products. In the present study, the effect of high hydrostatic pressure (HPP) treatment in combination with natural antioxidants (radish, beetroot, rosemary) and antimicrobial substances (“Medoliva”) on the quality parameters, changes in myoglobin and lipid oxidation of ground beef during storage was investigated. Significant increase in total myoglobin was found in the group with radish (C3) on the 5th day of storage, as well as a significant decrease in the percentage of deoxymyoglobin with increasing storage time in the groups with added radish (C3) and beetroot (C4). Furthermore, significant increase in the values of the redness (a*) in group C3 and decrease in the values of the yellowness (b*) in group C4 were found. The prolonged duration of storage lead to decrease in the water holding capacity (WHC) of the ground beef, as well as an increase in the a* and b* values of the meat on the 20th day, followed by a decrease in the values of the indicators on the 40th day of its storage. In general, with the exception of group C5 with addition of rosemary oil, high hydrostatic pressure treatment in combination with antioxidants did not inhibit lipid oxidation processes. With increasing duration of storage, the TBARS values in ground beef increased. [ABSTRACT FROM AUTHOR]

Suspensions of non-pathogenic Listeria innocua ATCC 33090 in water were exposed to different combinations of high hydrostatic pressure (HPP), pulsed electric field (PEF) and sonication treatments. Treatments were conducted individually, or in various combinations – sequential HPP-PEF; sequential PEF-HPP, simultaneous HPP-PEF, sequential HPP-sonication and sequential sonication-HPP. The greatest reduction by an individual treatment was obtained with HPP, wherein exposure to 400 MPa for 100 s resulted in an 8 log reduction in CFU. Both PEF (30 kV, 10 −3  s) and sonication (250s) treatments gave about 2 log reduction in the Listeria population. Sequentially applied HPP-PEF, and PEF-HPP treatments demonstrated mostly additive effects. Notably, however, a synergistic effect was observed when PEF and HPP were applied simultaneously. Combinations of HPP and sonication treatments demonstrated synergistic effects when HPP treatment was followed by sonication, but additive effects when sonication was followed by HPP. A relationship between Listeria innocua inactivation and increase in the suspension zeta potential was observed. However, protein content of the supernatant was found insignificant, indicating that leakage from cells were non-protein cell constituents. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus is responsible for a large spectrum of diseases, including staphylococcal food poisoning (SFP), due to its ability to produce enterotoxins. To prevent the development of SFP, effective food preservation methods are needed. High pressure processing (HPP) uses pressures, between 100 and 600 MPa, to inactivate pathogenic and spoilage microorganisms. In this study, HPP treatments (450 MPa and 600 MPa, both for 15 and 30 min, at 20 °C) were applied in three different strains of S. aureus in the stationary growth phase and reduction effectiveness was assessed. A non-enterotoxic strain ATCC 6538 and two enterotoxic strains 2153 MA (with enterotoxin A) and 2065 MA (with enterotoxin A, G, I) were used. It was verified that the non-enterotoxic strain was the most resistant to HPP, not being completely inactivated within 30 min at 600 MPa. Additionally, it was demonstrated that HPP had no effect on virulence factors (enterotoxins, β-hemolysin, lipase, lecithinase, coagulase, thermonuclease, catalase), and also in mannitol fermentation capacity and methicillin susceptibility. HPP treatments also proved to be less effective in the strain with higher carotenoids content (non-enterotoxic strain). The results of this study show that S. aureus HPP barotolerance might be related not only to the presence of enterotoxins but also to carotenoids level, although these two factors may not be the only mechanisms responsible for the distinct sensitivity/resistance to HPP shown by different strains of S. aureus . [ABSTRACT FROM AUTHOR]

In this work, the development of resistance and the recovery of growth after several consecutive cycles of high hydrostatic pressure (HPP) were for the first time evaluated in different strains of Staphylococcus aureus . Three strains of this important and highly resilient to HPP foodborne pathogen were used: a non-enterotoxigenic ATCC 6538 strain, treated with 600 MPa for 30 min at 20 °C, and the toxigenic strains 2153 MA (with enterotoxin A) and 2065 MA (with the enterotoxins A, G and I), treated with 600 MPa for 15 min at 20 °C. After the first treatment, surviving colonies were used to produce new bacterial cultures. This procedure was repeated nine times more for each bacterium or until total inactivation occurred. The inactivation profile of non-enterotoxic strain and the two enterotoxic strains did not change after consecutive cycles, but the toxic strain with three enterotoxins was completely inactivated after the fourth cycle. The three strains did not recover their viability after 14 days. The results indicate that HPP effectively inactivates non-toxigenic and toxigenic strains of S. aureus after a single treatment. The surviving bacteria did not develop resistance after 10 cycles of pressurization and did not recover their viability after 14 days of incubation. [ABSTRACT FROM AUTHOR]