Abstract Contamination of fresh produce with bacteria can occur during cultivation, harvest and post-harvest processing and the current sanitation approaches for post-harvest processing are not adequate for inactivation of pathogenic or spoilage bacteria that may be attached to the surface of fresh produce. This study evaluated the role of ultrasound with and without surfactants and sanitizers to improve decontamination of fresh produce and the impact of these treatments on the quality of fresh produce. Gram-positive bacterial strain Listeria innocua, and gram-negative bacterial strains Escherichia coli O157:H7 and Pseudomonas fluorescens were tested in this study. The reduction in bacterial concentration from inoculated leaf samples increased with an increase in ultrasound treatment time until 10 min for all the three strains. When compared to ultrasound treatment alone, combination of ultrasound treatment with surfactants did not significantly increase the removal of E. coli and L. innocua from the lettuce surfaces, however, the removal efficacy of P. fluorescens increased significantly under the same treatment conditions. The results of simultaneous washing of multiple leaves using ultrasound showed the net bacterial reduction from lettuce leaves decreased by approximately 0.5 log CFU/cm2 for all the selected strains compared to treatment of a single leaf. Similarly, combination of ultrasound with surfactants for simultaneous treatment of multiple leaves did not improve removal of E. coli and L. innocua from the surface of lettuce leaves, but improved removal of P. fluorescens by approximately 1 log unit when compared to ultrasound treatment alone. The evaluation of the risk of potential cross-contamination during ultrasound washing suggested ultrasound could significantly reduce the bacterial attachment to the uninoculated lettuce surface. Combination of ultrasound with adequate active free chlorine could prevent the transfer of E. coli and L. innocua cells from the inoculated leaf sample to uninoculated leaves. Evaluation of lettuce quality attributes in our study found that exposure to ultrasound treatment for less than 10 min had no significant effect on the quality of fresh lettuce. Thus, ultrasound treatment has a potential to be an alternative for maintaining the safety and quality of fresh produce during post-harvest processing.

中文翻译：

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在超声波辅助清洗新鲜农产品过程中，去污效果和降低交叉污染的风险

摘要 新鲜农产品在栽培、收获和收获后加工过程中可能会受到细菌污染，目前收获后加工的卫生方法不足以灭活可能附着在新鲜农产品表面的致病菌或腐败菌。本研究评估了超声波在使用和不使用表面活性剂和消毒剂的情况下改善新鲜农产品净化的作用以及这些处理对新鲜农产品质量的影响。本研究测试了革兰氏阳性菌株李斯特菌、革兰氏阴性菌株大肠杆菌 O157:H7 和荧光假单胞菌。对于所有三种菌株，随着超声处理时间的增加，接种叶样品中细菌浓度的降低增加，直到 10 分钟。与单独的超声处理相比，超声处理与表面活性剂的组合并未显着增加从生菜表面去除大肠杆菌和无害李斯特菌，但在相同处理条件下，荧光假单胞菌的去除效率显着增加。使用超声波同时清洗多片叶子的结果表明，与处理单片叶子相比，所有选定菌株的生菜叶子的净细菌减少量降低了约 0.5 log CFU/cm2。类似地，将超声波与表面活性剂结合用于同时处理多片叶子并没有改善从生菜叶子表面去除大肠杆菌和无害李斯特菌，但与单独超声波处理相比，荧光假单胞菌的去除率提高了大约 1 个对数单位. 对超声清洗过程中潜在交叉污染风险的评估表明，超声可以显着减少未接种生菜表面的细菌附着。超声与足够的活性游离氯相结合可以防止大肠杆菌和无害李斯特菌细胞从接种的叶子样品转移到未接种的叶子。在我们的研究中对生菜质量属性的评估发现，超声处理时间少于 10 分钟对新鲜生菜的质量没有显着影响。因此，超声波处理有可能成为在收获后加工过程中保持新鲜农产品安全和质量的替代方法。