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- Efficacy of Power Ultrasound Technology on the Reduction of Listeria monocytogenes and Salmonella enterica on Produce Matrices
- Biswas, Priya
Fresh produces are considered as ready-to-eat (RTE) and are minimally processed before the distribution to retailers and consumers. Fresh...
Show moreFresh produces are considered as ready-to-eat (RTE) and are minimally processed before the distribution to retailers and consumers. Fresh produce recalls are frequently linked with pathogenic bacteria like Salmonella enterica and Listeria monocytogenes because of minimal processing. This study evaluated the use of power ultrasound coupled with organic acids like citric, acetic, and lactic acid which are generally recognized as safe and often helps to maintain the quality and prolong the shelf life of fresh RTE fruits and vegetables.All the produce matrices which include cucumbers, romaine lettuce, tomatoes, and strawberry were inoculated with four-strain cocktails of rifampicin-resistant S. enterica or L. monocytogenes at approximately 8 log CFU/ matrix. The produce matrices were dried for 1 h and treated for 2 minutes using 2 % or 5 % citric, lactic, or malic acid. This treatment was conducted with or without power ultrasound treatment at 40 kHz. Samples were taken in sets of three and placed into a stomacher bags. The bag contained 225 ml of water or acid. Following a 2 min treatment period, the samples were placed in separate stomacher bags, each containing 225ml of BPB or BLEB, for S. enterica or L. monocytogenes respectively. Followed serial dilutions, samples were then plated on BHIARif plates. For each condition, triplicate samples were taken, and three separate trials were conducted. The use of Student's t-test allowed for the evaluation of population differences, with a significance level of p<0.05 being deemed significant. Cucumber, romaine lettuce, tomatoes, and strawberries treated with 5 % concentration of citric, lactic, and malic acids, with addition of ultrasound showed a greater result in reductions of S. enterica to populations of 5.54 ± 0.47, 4.54 ± 0.83, and 4.69 ± x 0.36, log CFU/cucumber, 6.66 ± 0.51, 4.12 ± 0.32, and 5.51 ± 0.68, log CFU/ lettuce, 4.38 ± 0. 47, 3.12, and 5.04 ± 0.37 log CFU/ tomato, 4.66 ± 0.49, 4.69 ± 0.06, and 6.22 ± 0.39, log CFU/ strawberries, respectively. For L. monocytogenes, 5 % concentration of acids with the addition of ultrasound resulted in populations of 7.69 ± 0.35, 6.04 ± 0.24, and 6.96 ± 0.41, log CFU/ cucumbers, 7.57 ± 0.12, 5.49 ± 0.55, and 5.78 ± 0.73 log CFU/ lettuce, 6.44 ± 0.13, 5.08 ± 0.12, and 6.04 ± 0.22 log CFU/ tomato, 6.16 ± 0.37, 5.18 ± 0.22, and 5.64 ± 0.50, log CFU/ strawberries, respectively. The most effective acid was lactic when compared with citric and malic acids. The objective of this study is to investigate the effectiveness of power ultrasound as a novel non-thermal processing technology, in order to contribute to the existing knowledge base on this topic.