Microbial Food Safety Research Unit, US Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, Wyndmoor, PA 19038, USA.
Food Microbiol. 2010 Feb;27(1):37-43. doi: 10.1016/j.fm.2009.07.016. Epub 2009 Jul 24.
Microbial cross-contamination either at home or production site is one of the major factors of causing contamination of foods and leading to the foodborne illness. The knowledge regarding Escherichia coli O157:H7 surface transfer on ready-to-eat (RTE) deli meat and the slicer used for slicing different RTE products are needed to ensure RTE food safety. The objectives of this study were to investigate and to model the surface cross-contamination of E. coli O157:H7 during slicing operation. A five-strain cocktail of E. coli O157:H7 was inoculated directly onto a slicer's round blade rim area at an initial level of ca. 4, 5, 6, 7 or 8 log CFU/blade (ca. 3, 4, 5, 6 or 7 log CFU/cm(2) of the blade edge area), and then the RTE deli meat (ham) was sliced to a thickness of 1-2 mm. For another cross-contamination scenario, a clean blade was initially used to slice ham which was pre-surface-inoculated with E. coli O157:H7 (ca. 4, 5, 6, 7 or 8 log CFU/100 cm(2) area), then, followed by slicing un-inoculated ham. Results showed that the developed empirical models were reasonably accurate in describing the transfer trend/pattern of E. coli O157:H7 between the blade and ham slices when the total inoculum level was >or=5 log CFU on the ham or blade. With an initial inoculum level at <or=4 log CFU, the experimental data showed a rather random microbial surface transfer pattern. The models, i.e., a power equation for direct-blade-surface-inoculation, and an exponential equation for ham-surface-inoculation are microbial load and sequential slice index dependent. The surface cross-contamination prediction of E. coli O157:H7 for sliced deli meat (ham) using the developed models were demonstrated. The empirical models may provide a useful tool in developing the RTE meat risk assessment.
微生物在家中或生产现场的交叉污染是导致食品污染和食源性疾病的主要因素之一。为确保即食（RTE）熟食食品安全，需要了解大肠杆菌 O157:H7 在准备即食（RTE）熟食肉和用于切割不同 RTE 产品的切片机表面的转移。本研究的目的是研究和建立大肠杆菌 O157:H7 在切片操作过程中的表面交叉污染模型。将五株大肠杆菌 O157:H7 鸡尾酒直接接种到切片机的圆形刀片边缘区域，初始水平约为 4、5、6、7 或 8 log CFU/刀片（刀片边缘区域约为 3、4、5、6 或 7 log CFU/cm(2)），然后将 RTE 熟食肉（火腿）切成 1-2 毫米厚的薄片。在另一种交叉污染情况下，先用干净的刀片将事先用大肠杆菌 O157:H7 表面接种（约 4、5、6、7 或 8 log CFU/100 cm(2) 区域）的火腿切片，然后再将未接种的火腿切片。结果表明，当火腿或刀片上的总接种物水平>或=5 log CFU 时，开发的经验模型在描述大肠杆菌 O157:H7 在刀片和火腿切片之间的转移趋势/模式方面是合理准确的。初始接种物水平<或=4 log CFU 时，实验数据显示微生物表面转移模式相当随机。这些模型，即直接刀片表面接种的幂方程和火腿表面接种的指数方程，与微生物负荷和连续切片指数有关。使用开发的模型对切片熟食（火腿）中大肠杆菌 O157:H7 的表面交叉污染进行了预测。经验模型可为开发即食肉类风险评估提供有用工具。
