Department of Food Science, Cornell University, Geneva, NY 14456, USA.
J Food Prot. 2012 Jul;75(7):1198-206. doi: 10.4315/0362-028X.JFP-12-009.
Produce-associated foodborne illnesses outbreaks have highlighted the need for more effective decontamination methods to ensure the safety of fresh produce. The main objective of this study was to evaluate the individual and combined efficacies of germicidal UV light (12.5 to 500 mJ/cm(2)), acidified sodium hypochlorite (ASC 10 to 200 ppm), and mild heat (40 to 50°C) for decontaminating green onions and baby spinach infected with Escherichia coli O157:H7. Samples were inoculated by spot and dip inoculation methods to mimic surface and infiltrated E. coli O157:H7 contamination, respectively. In green onions and baby spinach, the individual efficacies of UV, ASC, and mild-heat treatments varied based on the produce type and contamination method. Following analysis of the efficacies of the single treatments, a combined treatment with 125 mJ/cm(2) UV and 200 ppm of ASC at 50°C was selected for spot-inoculated green onions, and a combined treatment with 125 mJ/cm(2) UV and 200 ppm of ASC at 20°C was selected for spot- and dip-inoculated baby spinach. While a >5-log reduction was achieved with the combination treatment for spot-inoculated green onions with an initial contamination level of 7.2 log CFU per spot, the same treatment reduced E. coli O157:H7 populations below the detection limit (<1 log) on green onions spot inoculated at a lower contamination level (4.3 log CFU per spot). On spot- and dip-inoculated baby spinach, the combined treatment reduced E. coli O157:H7 populations by 2.8 log CFU per spot and 2.6 log CFU/g, respectively. The combined treatment of 500 mJ/cm(2) UV and 200 ppm of ASC at 50°C selected for the decontamination of dip-inoculated green onions resulted in a 2.2-log CFU/g reduction. These findings suggest that when foodborne pathogens contaminate produce and subsequently infiltrate, attach to, or become localized into protected areas, the individual or combined applications of UV, ASC, and mild-heat treatments have limited decontamination efficacies on both green onions and baby spinach (<3 log). However, treatments combining UV, ASC, and mild heat could be a promising application for reducing pathogen populations (>5 log) on E. coli O157:H7 surface-contaminated green onions. This study also highlights the importance of developing and optimizing produce-specific decontamination methods to ensure the safety of fresh produce commodities.
生产相关的食源性疾病暴发突出表明，需要更有效的消毒方法来确保新鲜农产品的安全。本研究的主要目的是评估杀菌紫外线（12.5 至 500 mJ/cm(2)）、酸化次氯酸钠（ASC 10 至 200 ppm）和温和加热（40 至 50°C）单独和联合使用对受大肠杆菌 O157:H7 污染的青葱和婴儿菠菜的消毒效果。通过点涂接种方法对样品进行接种，分别模拟表面和渗透的大肠杆菌 O157:H7 污染。在青葱和婴儿菠菜中，紫外线、ASC 和温和加热处理的单独效果取决于产品类型和污染方法。在分析了单一处理的效果后，选择 125 mJ/cm(2)紫外线和 50°C 下 200 ppm ASC 的联合处理用于点涂接种的青葱，选择 125 mJ/cm(2)紫外线和 200 ppm ASC 的联合处理用于点涂和浸涂接种的婴儿菠菜。对于初始污染水平为每点 7.2 log CFU 的点涂接种青葱，组合处理可实现 >5-log 的减少，但对于污染水平较低（每点 4.3 log CFU）的点涂接种青葱，相同的处理可将大肠杆菌 O157:H7 降低至检测限以下（<1 log）。对于点涂和浸涂接种的婴儿菠菜，联合处理分别使大肠杆菌 O157:H7 的数量减少了每点 2.8 log CFU 和每克 2.6 log CFU。选择用于消毒浸涂接种青葱的 500 mJ/cm(2)紫外线和 200 ppm ASC 在 50°C 的组合处理使每克减少 2.2-log CFU。这些发现表明，当食源性病原体污染农产品并随后渗透、附着或定位于保护区域时，紫外线、ASC 和温和加热处理的单独或联合应用对青葱和婴儿菠菜的消毒效果有限（<3 log）。然而，紫外线、ASC 和温和加热的处理组合可能是减少大肠杆菌 O157:H7 表面污染青葱上的病原体数量（>5 log）的有前途的应用。本研究还强调了开发和优化针对特定农产品的消毒方法以确保新鲜农产品安全的重要性。
