1 School of Animal and Comparative Biomedical Sciences, University of Arizona, 1117 East Lowell Street, Tucson, Arizona 85721.
2 Yuma Agricultural Center, University of Arizona, 6425 West 8th Street, Yuma, Arizona 85364, USA.
J Food Prot. 2019 Mar;82(3):454-462. doi: 10.4315/0362-028X.JFP-18-317.
Contaminated coring tools may transfer bacteria to iceberg lettuce. The efficiency of coring tool design modifications in reducing bacterial transfer to lettuce heads was evaluated under simulated field operations. The standard coring tool consists of a stainless steel cylindrical tube welded to a tab that is inserted into a plastic handle. Design modifications included removal of the welded portion, incorporation of a shorter front straight bottom edge, or an angled bottom edge toward the front. In the first study, coring tools of four different designs were inoculated by dipping in a tryptic soy broth (TSB) suspension that contained 8.85 Log CFU/mL of Escherichia coli K-12 and then were used to core 100 lettuce heads, consecutively. Use of the standard tool resulted in 91% ± 9% positive lettuce heads. Removing the welded surface from the standard tool resulted in the highest reduction of E. coli transfer (44% ± 11.9% positive lettuce heads, P < 0.05), whereas incorporation of a short front straight edge with no welding resulted in 65.6% ± 5.6% of the cored lettuce heads being positive for E. coli. Removal of the welded surface resulted in a 40% decrease in E. coli contamination among the last 20 cored lettuce heads (81 to 100), which indicates that coring tool design modifications resulted in reduced cross-contamination. In the second study, the transfer of Salmonella to coring tools after their immersion in rinsing solutions was evaluated using imaging. The tools were dip inoculated for 2 min in water, water with lettuce extract, or TSB containing 7 Log CFU/mL bioluminescent Salmonella Newport; they were then imaged to observe spatial distribution of bacteria. There was greater retention and spatial distribution of Salmonella on the surface of tools immersed in water containing lettuce extract than in TSB and water. The results of the second study indicate that rinsing solutions that contain lettuce particulate and organic load could facilitate cross-contamination of Salmonella Newport to tool surfaces.
受污染的取芯工具可能会将细菌转移到冰山生菜上。在模拟田间操作下，评估了取芯工具设计改进在减少细菌转移到生菜头中的效率。标准取芯工具由焊接在插入塑料手柄的片上的不锈钢圆柱形管组成。设计改进包括去除焊接部分、采用较短的前直底部边缘或朝向前部的倾斜底部边缘。在第一项研究中，将四个不同设计的取芯工具浸入含有 8.85 Log CFU/mL 大肠杆菌 K-12 的胰蛋白酶大豆肉汤 (TSB) 悬浮液中进行接种，然后连续取芯 100 个生菜头。使用标准工具导致 91%±9%的生菜头呈阳性。从标准工具上去除焊接表面导致大肠杆菌转移的减少率最高（44%±11.9%的取芯生菜头呈阳性，P<0.05），而采用无焊接的短前直边导致 65.6%±5.6%的取芯生菜头呈大肠杆菌阳性。去除焊接表面使最后 20 个取芯生菜头中的大肠杆菌污染减少了 40%（81 到 100），这表明取芯工具设计的改进导致了交叉污染的减少。在第二项研究中，使用成像评估了取芯工具在浸入冲洗溶液后对沙门氏菌的转移情况。工具在水中、含有生菜提取物的水中或含有 7 Log CFU/mL 生物发光沙门氏菌纽波特的 TSB 中浸泡 2 分钟进行浸蘸接种；然后对工具进行成像以观察细菌的空间分布。在含有生菜提取物的水中浸泡的工具表面上，沙门氏菌的保留和空间分布比 TSB 和水更大。第二项研究的结果表明，含有生菜颗粒和有机负荷的冲洗溶液可能会促进沙门氏菌纽波特交叉污染到工具表面。
