Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824, USA.
J Food Prot. 2014 Mar;77(3):380-7. doi: 10.4315/0362-028X.JFP-13-314.
Salmonella transfer during washing and roller conveying of inoculated tomatoes was quantified using a pilot scale tomato packing line equipped with plastic, foam, or brush rollers. Red round tomatoes (2.3 kg) were dip inoculated with Salmonella enterica serovar Typhimurium LT2 (avirulent) (4 log CFU/g), air dried for 2 h, and then washed in sanitizer-free water for 2 min. Inoculated tomatoes were then passed single file over a 1.5-m conveyor equipped with plastic, foam, or brush rollers followed by 25 previously washed uninoculated tomatoes. Tomato samples were collected after 2 min of both washing and roller conveying, with all 25 uninoculated tomatoes collected individually after conveying. Roller surface samples were collected before and after conveying the uninoculated tomatoes. Both tomato and surface samples were quantitatively examined for Salmonella by direct plating or membrane filtration using xylose lysine Tergitol 4 agar. Regardless of the roller type, Salmonella populations on inoculated tomatoes did not significantly (P < 0.05) decrease during contact with the roller conveyors. After conveying uninoculated tomatoes over contaminated foam rollers, 96% of the 25 tomatoes were cross-contaminated with Salmonella at >100 CFU per tomato. With plastic rollers, 24 and 76% of tomatoes were cross-contaminated with Salmonella at 10 to 100 and 1 to 10 CFU per tomato, respectively. In contrast, only 8% of 25 tomatoes were cross-contaminated with brush rollers with Salmonella populations of 1 to 10 CFU per tomato. Overall, cross-contamination was greatest with foam, followed by plastic and brush rollers (P < 0.05). Adding peroxyacetic acid or chlorine to the wash water significantly decreased cross-contamination during tomato conveying, with chlorine less effective in controlling Salmonella on foam compared with plastic and brush rollers.
采用配备有塑料、泡沫或毛刷辊的试验规模番茄包装线，定量评估了接种番茄在洗涤和辊筒输送过程中的沙门氏菌转移情况。将红圆番茄（2.3 千克）浸入含有无毒性鼠伤寒沙门氏菌 LT2（4 对数 CFU/g）的溶液中进行蘸菌接种，风干 2 小时，然后在无菌水中清洗 2 分钟。接种后的番茄随后单排通过配备有塑料、泡沫或毛刷辊的 1.5 米长的传送装置，然后是 25 个之前已清洗的未接种的番茄。在洗涤和辊筒输送 2 分钟后，采集番茄样本，在传送完成后，逐个采集所有 25 个未接种的番茄。在传送未接种番茄前后，采集辊筒表面样本。采用木糖赖氨酸 Tergitol 4 琼脂通过直接平板计数或膜过滤法，对番茄和表面样本中的沙门氏菌进行定量检测。无论采用哪种类型的辊筒，接种番茄与辊筒接触时，其表面的沙门氏菌数量均未显著（P＜0.05）减少。在受污染的泡沫辊筒上输送未接种的番茄后，25 个番茄中有 96%受到沙门氏菌交叉污染，每个番茄的污染水平＞100 CFU。采用塑料辊筒时，分别有 24%和 76%的番茄受到沙门氏菌交叉污染，污染水平分别为 10 至 100 CFU/个和 1 至 10 CFU/个。相比之下，采用毛刷辊筒时，仅有 8%的 25 个番茄受到沙门氏菌污染，每个番茄的污染水平为 1 至 10 CFU。总体而言，泡沫辊筒的交叉污染最严重，其次是塑料辊筒和毛刷辊筒（P＜0.05）。在番茄输送过程中，向洗涤水中添加过氧乙酸或氯可显著降低交叉污染，而与塑料和毛刷辊筒相比，氯对控制泡沫辊筒上的沙门氏菌效果较差。
