School of Food Science and Irrigated Agriculture Research and Extension Center, Washington State University, Prosser, WA, United States.
Department of Food Science and Technology, University of Georgia, Athens, GA, United States.
Sci Total Environ. 2023 Aug 10;885:163884. doi: 10.1016/j.scitotenv.2023.163884. Epub 2023 May 3.
Preharvest agricultural water has been recognized as one of the routes of contamination for foodborne pathogens during fruit and vegetable production. Several strategies have been proposed to reduce the risk of pathogens, including preharvest water chemigation, but literature is lacking with regards to microbiological inactivation of common bacterial foodborne pathogens associated with fresh produce contamination, Salmonella enterica, Shiga-toxigenic Escherichia coli (STEC), and Listeria monocytogenes, in surface irrigation water after exposure to chlorine and peracetic acid (PAA). Surface water supplied by a local irrigation district was collected over the summer of 2019. Water was autoclaved, divided into 100 mL samples, and inoculated with a cocktail of five Salmonella, STEC, or Listeria monocytogenes strains or a single strain non-pathogenic E. coli. Samples were then treated with 3, 5, or 7 ppm of free chlorine or PAA, and surviving populations were evaluated using a time-kill assay. A first-order kinetic model was used to fit the inactivation data and obtain the D-values. A secondary model was used to explain the changes due to the type of water, treatment, and microorganism. At a concentration of 3 ppm, the observed and predicted D-values of free chlorine treatments were higher than that of PAA treatments for ground and surface water. Results indicated that PAA was more effective inactivating bacteria than sodium hypochlorite at concentrations of 3 and 5 ppm for both water sources (surface and ground). However, at 7 ppm, the effectiveness of PAA and sodium hypochlorite showed no statistically significant difference for both surface and groundwater. Findings will provide information regarding efficacy of chemical sanitizers like chlorine and PAA for inactivation of Salmonella, Listeria, and STEC in surface water from which treatments can be derived. Ultimately benefitting growers in the selection of an appropriate method for in-field treatment of irrigation water if deemed necessary.
在水果和蔬菜生产过程中，收获前农业用水已被认为是食源性病原体污染的途径之一。已经提出了几种降低病原体风险的策略，包括收获前水化学灌溉，但缺乏关于氯和过氧乙酸 (PAA) 暴露后表面灌溉水中常见与新鲜农产品污染相关的食源性病原体细菌，即肠炎沙门氏菌、产志贺毒素大肠杆菌 (STEC) 和单核细胞增生李斯特菌的微生物灭活的文献。2019 年夏天，从当地灌溉区收集了地表水。将水进行高压灭菌，分成 100 毫升的样本，并接种含有五种肠炎沙门氏菌、STEC 或单核细胞增生李斯特菌的混合物或单一非致病性大肠杆菌菌株。然后，用 3、5 或 7 ppm 的游离氯或 PAA 处理样品，并使用时间杀灭试验评估存活的菌群。使用一级动力学模型拟合失活动力学数据并获得 D 值。使用二次模型来解释由于水源、处理和微生物类型而导致的变化。在 3 ppm 的浓度下，观察到的和预测的游离氯处理的 D 值高于 PAA 处理的地面和地表水。结果表明，在 3 和 5 ppm 的浓度下，PAA 比次氯酸钠更有效地灭活两种水源（地表水和地下水）中的细菌。然而，在 7 ppm 时，PAA 和次氯酸钠的有效性在地面和地下水中均无统计学差异。这些发现将提供有关氯和 PAA 等化学消毒剂在灭活表面水中的沙门氏菌、李斯特菌和 STEC 的功效的信息，从中可以得出处理方法。如果有必要，这最终将使种植者受益于选择适当的田间灌溉水处理方法。
