Intervention Technologies to Enhance the Microbiological Safety of Fresh Produce

与新鲜水果和蔬菜有关的召回和食源性疾病暴发的数量继续增加。最值得注意的是与莴苣和哈密瓜有关的食源性疾病的爆发，这些食物似乎特别容易受到污染。迄今为止，主要的方法是将食品安全倡议的重点放在初级生产阶段和收获后清洗阶段，目的是消除田间获得的污染。虽然诸如绿叶蔬菜协议之类的初级生产倡议提高了食品安全标准，但作物生产的开放性使防止污染成为不可能。以类似的方式，已经确定收获后的洗涤是有限的（最多减少1-2 log cfu），并且会造成更大的交叉污染而不是去污的风险。拟议的研究项目将致力于开发收获后的干预措施，通过净化和预防交叉污染来提高新鲜农产品的微生物安全性，从而实现将相关病原体减少5 log cfu的食品安全目标。第一阶段将通过将抗微生物羟基自由基引入顶空来减少农产品在保存和运输过程中的污染。产生的羟基自由基不具有很强的抗菌活性，但可以在长时间暴露后灭活病原体，因此与新鲜农产品的储存和运输兼容。通过使用电解水或UV：过氧化氢（高级氧化工艺）的过程中去污技术，将洗涤步骤中的交叉污染事件降到最低。这两种方法都具有有效的抗菌活性，而不会产生显著的消毒副产物。这些表面将集中在传送带和切片装置上，这些装置是交叉污染的场所。虽然在洗涤水中预计会有一定程度的去污，但主要目的是通过使用一种新型的酸化壳聚糖消毒剂来减少交叉污染事件，这种消毒剂将灭活病原体并凝固有机负载。最后，基于高级氧化工艺的洗后去污步骤将用于去除残留的病原体水平。在这里，研究将着眼于开发一个连续的AOP处理单元，以使用批处理反应器取得的成功为基础。反应器将以紫外线隧道为基础，过氧化氢雾被引入顶空。每种干预措施将在病原体（沙门氏菌，产志贺毒素大肠杆菌和单核增生李斯特菌的五种染色鸡尾酒）减少方面进行优化，同时保持产品质量（视觉，质地）。每个干预措施将在最大限度地减少对数计数方面进行优化，而不会对产品质量产生不利影响。这项研究将通过减少新鲜农产品上病原体的发生率而使该行业受益。虽然目前的研究将集中在生菜和哈密瓜上，但可以设想同样的方法可以应用于其他类型的农产品。此外，将优化干预步骤并建立关键限制，以促进真正的HACCP系统。正在应用的技术目前是可用的或接近市场，因此可以很容易地由新鲜农产品行业实施。

The number of recalls and foodborne illness outbreaks linked to fresh fruit and vegetables continues to increase. Most noteworthy have been outbreaks of foodborne illness linked to lettuce and cantaloupes which appear especially susceptible to contamination. To date, the main approach has been to focus food safety initiatives at the primary production stage and also at the post-harvest wash stage that is designed to remove field acquired contamination. Although primary production initiatives such as the leafy greens agreement have enhanced food safety standards the open nature of crop production makes it impossible to prevent contamination. In a similar manner, it is well established that post-harvest washing is limited (1-2 log cfu reduction at best) and poses a greater risk of cross-contaminating produce rather than decontamination. The proposed research program will be directed towards developing post-harvest interventions to enhance the microbiological safety of fresh produce through decontamination and prevention of cross-contamination thereby meeting a Food Safety Objective of a 5 log cfu reduction of relevant pathogens. The first stage will reduce contamination of produce during holding and transport by introducing antimicrobial hydroxyl radicals into the headspace. Hydroxy radicals generated do not have strong antimicrobial activity but can inactivate pathogens over long exposure periods hence compatible with storage and transport of fresh produce. Cross-contamination events up to the wash step will minimized through in-process decontamination technologies using electrolyzed water or UV:hydrogen peroxide (Advanced Oxidative Process). Both approaches have the benefits of potent antimicrobial activity without producing significant disinfection byproducts. The surfaces will focus on conveyors and slicing units which are established cross-contamination sites. Although a degree of decontamination is expected in the wash water the main aim is to reduce cross-contamination events through using a novel acidified chitosan based sanitizer that will inactivate pathogens and also coagulate organic loading. Finally, a post-wash decontamination step based on using Advanced Oxidative Process will be applied to remove residual pathogen levels. Here, the research will be directed towards developing a continuous AOP treatment unit to build on the success achieved using a batch reactor. The reactor will be based on a UV tunnel with hydrogen peroxide mist being introduced into the headspace. Each intervention will be optimized in terms of pathogen (five stain cocktail of Salmonella, Shiga Toxin Producing Escherichia coli and Listeria monocytogenes) reduction whilst maintaining product quality (visual, texture). Each intervention will be optimized in terms of maximal log count reduction with no detrimental effects on product quality. The research will benefit the industry by reducing the incidence of pathogens on fresh produce. Although the current study will focus on lettuce and cantaloupes it can be envisaged that the same approach could be applied to other produce types. Moreover, the intervention steps will be optimized and critical limits established to facilitate a true HACCP system. The technologies being applied are currently available or near market so can be readily implemented by the fresh produce industry.