Key Laboratory of Food Nutrition and Safety (Tianjin University of Science & Technology), Ministry of Education, Tianjin 300457, China; U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, PA 19038, USA.
Int J Food Microbiol. 2013 Sep 16;166(3):356-63. doi: 10.1016/j.ijfoodmicro.2013.07.021. Epub 2013 Aug 3.
Some soft fruit, such as tree-ripened apricots, cannot be washed with aqueous sanitizers, due to their innate softness and delicate surfaces. In this study, ultraviolet-C (UV-C) light was investigated for its efficacy in inactivating 4-5 individual strains of Escherichia coli O157:H7 and Salmonella spp. on apricots, in addition to a four-strain composite of Shiga toxin-negative E. coli O157:H7 and a cocktail of three attenuated strains of Salmonella Typhimurium and Salmonella Typhimurium LT2. Also, the survival of E. coli O157:H7 and Salmonella spp. after exposure to 74 and 442 mJ/cm² of UV-C was evaluated during post-UV storage at 2 and 20 °C. The fruit was spot inoculated and the areas (ca. 1.5 cm²) of fruit surface with the inoculated bacteria were exposed to UV-C at 7.4 mW/cm². E. coli O157:H7 and Salmonella spp. populations decreased rapidly (1-2 logs) (P<0.05) with increasing UV-C doses of 0 to 74 mJ/cm². Further increases in UV-C dosage achieved only limited additional reductions in bacterial populations. Shiga toxin-negative bacteria and attenuated S. Typhimurium strains, along with S. Typhimurium LT2, responded similarly to corresponding pathogenic E. coli O157:H7 and Salmonella spp. During storage at 2 or 20 °C, populations of pathogenic E. coli O157:H7 and Salmonella spp. on untreated fruit decreased slowly; however, populations on fruit treated with 442 mJ/cm² decreased rapidly at both temperatures. After 8 days at 20 °C or 21 days at 2 °C, E. coli O157:H7 and Salmonella spp. populations on UV-C treated fruit were at least 2 log CFU/g lower than on non-treated controls. Our results suggest that surface-inoculated bacteria survived poorly following UV-C treatment of apricots.
一些软水果，如成熟的李子，由于其天生的柔软和脆弱的表面，不能用含水分的消毒剂清洗。在这项研究中，紫外线-C（UV-C）光被用于研究其在灭活李子上的 4-5 种大肠杆菌 O157:H7 和沙门氏菌的功效，此外还有一株不含志贺毒素的大肠杆菌 O157:H7 和三株减毒的鼠伤寒沙门氏菌和鼠伤寒沙门氏菌 LT2 的复合菌株。此外，还评估了在 2 和 20°C 下储存期间，暴露于 74 和 442 mJ/cm²的 UV-C 后，大肠杆菌 O157:H7 和沙门氏菌在 UV-C 后的存活情况。将水果进行点接种，用接种细菌的水果表面区域（约 1.5 cm²）暴露在 7.4 mW/cm²的 UV-C 下。大肠杆菌 O157:H7 和沙门氏菌的数量迅速减少（1-2 对数）（P<0.05），随着 UV-C 剂量从 0 增加到 74 mJ/cm²。进一步增加 UV-C 剂量只能使细菌数量略有进一步减少。非产志贺毒素的细菌和减毒的鼠伤寒沙门氏菌菌株与鼠伤寒沙门氏菌 LT2 一样，对相应的致病性大肠杆菌 O157:H7 和沙门氏菌的反应相似。在 2 或 20°C 下储存时，未经处理的水果上致病性大肠杆菌 O157:H7 和沙门氏菌的数量缓慢减少；然而，在 442 mJ/cm² 处理的水果上，两种温度下的数量都迅速减少。在 20°C 下 8 天或 2°C 下 21 天后，UV-C 处理过的水果上的大肠杆菌 O157:H7 和沙门氏菌的数量比未经处理的对照至少低 2 个对数 CFU/g。我们的结果表明，经 UV-C 处理的李子表面接种的细菌存活能力较差。
