Nestlé Research Center, Institute of Food Safety and Analytical Science, CH 1000, Lausanne 26, Switzerland.
Institute of Nutrition and Functional Foods, Université Laval, Quebec, Quebec G1V 0A6, Canada.
Int J Food Microbiol. 2018 Jun 20;275:8-16. doi: 10.1016/j.ijfoodmicro.2018.03.016. Epub 2018 Mar 26.
Outbreaks of foodborne illness associated with berries often involve contamination with hepatitis A virus (HAV) and norovirus but also bacteria such as Escherichia coli O157:H7 and parasites such as Cyclospora caytanensis. We evaluated the applicability of UV-C to the inactivation of pathogens on strawberries, raspberries and blueberries. Our three-step approach consisted of assessing the chemical safety of UV-C-irradiated berries, evaluating the sensory quality after UV-C treatment and finally studying the inactivation of the target microorganisms. Treatments lasting up to 9 min (4000 mJ cm) did not produce detectable levels of furan (<5 μg/kg), a known photolysis product of fructose with genotoxic activity and thus were assessed to be toxicologically safe. No effect on taste or appearance was observed, unless treatment was excessively long. 20 s of treatment (an average fluence of ~ 212 mJ cm) reduced active HAV titer by >1 log unit in 95% of cases except on frozen raspberries, while 120 s were required to inactivate murine norovirus to this extent on fresh blueberries. The mean inactivation of HAV and MNV was greater on blueberries (2-3 log) than on strawberries and raspberries (<2 log). MNV was more sensitive on fresh than on frozen berries, unlike HAV. Inactivation of Salmonella, E. coli O157:H7 and Listeria monocytogenes was poor on all three berries, no treatment reducing viable counts by >1 log unit. In most matrices, prolonging the treatment did not improve the result to any significant degree. The effect was near its plateau after 20 s of treatment. These results provide insight into the effectiveness of UV-C irradiation for inactivating bacterial and viral pathogens and surrogates on fresh and frozen berries having different surface types, under different physical conditions and at different levels of contamination. Overall they show that UV-C as single processing step is unsuitable to inactivate significant numbers of foodborne pathogens on berries.
与浆果相关的食源性疾病爆发通常涉及甲型肝炎病毒（HAV）和诺如病毒的污染，但也涉及大肠杆菌 O157:H7 和环孢子虫等细菌。我们评估了 UV-C 对草莓、覆盆子和蓝莓中病原体的灭活适用性。我们的三步法包括评估 UV-C 辐照浆果的化学安全性、评估 UV-C 处理后的感官质量，最后研究目标微生物的灭活情况。持续时间不超过 9 分钟（4000mJ/cm）的处理不会产生可检测水平的糠醛（<5μg/kg），糠醛是果糖的已知光解产物，具有遗传毒性，因此被评估为具有毒理学安全性。除非处理时间过长，否则不会对味道或外观产生影响。20 秒的处理（平均辐照剂量约为 212mJ/cm）使 95%的情况下活性 HAV 滴度降低了>1 个对数单位，除了冷冻覆盆子外，而在新鲜蓝莓上需要 120 秒才能达到这种程度的鼠诺如病毒失活。HAV 和 MNV 的平均灭活在蓝莓（2-3 个对数）上大于草莓和覆盆子（<2 个对数）。与 HAV 不同，MNV 在新鲜浆果上比在冷冻浆果上更敏感。三种浆果上，对沙门氏菌、大肠杆菌 O157:H7 和李斯特菌的失活效果都很差，没有一种处理方法能使活菌数减少>1 个对数单位。在大多数基质中，延长处理时间并不能显著提高效果。处理 20 秒后，效果接近平台期。这些结果为了解 UV-C 照射对不同表面类型的新鲜和冷冻浆果中细菌和病毒病原体及其替代品的灭活效果提供了参考，这些浆果的物理条件不同，污染程度不同。总的来说，它们表明 UV-C 作为单一处理步骤不适合在浆果上灭活大量食源性病原体。
