Cold atmospheric gas plasma treatment (CAP) is an alternative approach for the decontamination of fresh and minimally processed food. In this study, the effects of growth phase, growth temperature and chemical treatment regime on the inactivation of Salmonella enterica serovar Typhimurium (S. Typhimurium) by Nitrogen CAP were examined. Furthermore, the efficacy of CAP treatment for decontaminating lettuce and strawberry surfaces and potato tissue inoculated with S. Typhimurium was evaluated. It was found that the rate of inactivation of S. Typhimurium was independent of the growth phase, growth temperature and chemical treatment regime. Under optimal conditions, a 2 min treatment resulted in a 2.71 log-reduction of S. Typhimurium viability on membrane filters whereas a 15 min treatment was necessary to achieve 2.72, 1.76 and 0.94 log-reductions of viability on lettuce, strawberry and potato, respectively. We suggest that the differing efficiency of CAP treatment on the inactivation of S. Typhimurium on these different types of fresh foods is a consequence of their surface features. Scanning electron microscopy of the surface structures of contaminated samples of lettuce, strawberry and potato revealed topographical features whereby S. Typhimurium cells could be protected from the active species generated by plasma.
A multistate outbreak of Salmonella enterica serovar Typhimurium recently occurred in the USA, which was traced back to various food products made with contaminated peanut butter. This study was conducted to investigate the efficacy of radio-frequency (RF) heating to inactivate S. Typhimurium and Escherichia coli O157:H7 in peanut butter cracker sandwiches using creamy and chunky commercial peanut butter and to determine the effect on quality by measuring color changes and sensory evaluation. Samples were treated for a maximum time of 90 s in a 27.12 MHz RF heating system. Samples were prepared in the form of peanut butter cracker sandwiches and placed in the middle of two parallel-plate electrodes. After 90 s of RF treatment, the log reductions of S. Typhimurium and E. coli O157:H7 were 4.29 and 4.39 log CFU/g, respectively, in creamy peanut butter. RF treatment of chunky peanut butter for 90 s also significantly (P < 0.05) reduced levels of S. Typhimurium and E. coli O157:H7 by 4.55 log CFU/g and 5.32 log CFU/g. Color values and sensory characteristics of the RF treated peanut butter and crackers were not significantly (P > 0.05) different from the control. These results suggest that RF heating can be applied to control pathogens in peanut butter products without affecting quality.
The effects of prior simultaneous pH (3.0–8.0), water activity, aw (0.93–0.99) and temperature (3.0–62.0 °C) stresses on injury and subsequent resistance of Salmonella Enteritidis to acid (pH 3.78, 25 °C) and heating (pH 3.78, 55 °C) in apple juice were determined. Injury rates were significantly (P < 0.05) influenced by the linear effects of aw and temperature. Exposure to combinations (pH 4.0, aw 0.98, 15 °C) and (pH 5.5, aw 0.99, 32.5 °C) resulted in acid adaptation. Only the linear influence of prior aw stress significantly affected the subsequent acid resistance. Heat resistance was greatest after previous exposure to pH, aw and temperature ranges of 4.0–5.5, 0.96–0.98, and 15–50 °C, respectively. None of the stress factors significantly influenced subsequent heat resistance. These results provide a more realistic simulation of the effects of environmental stress factors on the behavior of S. Enteritidis in food and food processing ecologies; and contribute in further understanding the behavior of the pathogen for the improvement of evaluation and control of safety of apple juice and similar products.
FoodWorld 