Division of Food Processing Science and Technology, U.S. Food and Drug Administration, Bedford Park, Illinois 60501.
Institute for Food Safety and Health, Illinois Institute of Technology, Bedford Park, Illinois 60501.
J Food Prot. 2022 Aug 1;85(8):1128-1132. doi: 10.4315/JFP-22-072.
Listeria monocytogenes is a foodborne pathogen associated with fresh produce vectors such as leafy greens. Recent outbreaks and recalls associated with red cabbage-containing salads have brought attention to this food commodity. Although data on the proliferation of L. monocytogenes are available for different varieties of whole and cut white cabbage, no information is available on the fate of this pathogen on red cabbage. The aim of this study was therefore to explore the survival of L. monocytogenes on cut red cabbage (Brassica oleracea L. var. capitata f. rubra) during storage at different temperatures. Red cabbage was cut into pieces (5 by 4 cm) and spot inoculated with a six-strain cocktail of rifampin-resistant L. monocytogenes, resulting in an initial inoculation level of 4 log CFU/g. Samples were stored at 5 or 10°C for 14 days or at 25°C for 7 days. At intervals during storage, L. monocytogenes was enumerated by homogenization of cabbage with Butterfield's phosphate buffer, and serial dilutions were plated onto brain heart infusion agar supplemented with rifampin. No growth of L. monocytogenes was observed on cut red cabbage during storage at 5°C, and only minimal proliferation was observed at the higher temperatures. Significant population increases of 0.58 and 1.07 log CFU/g were determined after 3 days of storage at 10 and 25°C, respectively; however, a significant decrease of 0.77 log CFU/g from 3 to 14 days was also observed at 10°C. The modeled growth rates for L. monocytogenes on cut red cabbage stored at 5 and 10°C were 0.11 ± 0.03 and 0.27 ± 0.07 log CFU/g/day, with calculated times to a 1-log CFU/g increase of 9.51 and 3.70 days, respectively; however, L. monocytogenes did not achieve a 1-log increase at either temperature in this study. At 25°C, the modeled growth rate of L. monocytogenes on cut red cabbage was 1.15 ± 0.36 log CFU/g, leading to a calculated and an observed 1-log increase in 0.87 and 3.00 days, respectively. Results from this study aid in understanding the fate of L. monocytogenes on cut red cabbage during storage at different temperatures.
单核细胞增生李斯特菌是一种食源性病原体，与叶类蔬菜等新鲜农产品载体有关。最近与含有红甘蓝的沙拉有关的爆发和召回事件引起了人们对这种食品的关注。尽管有关于整个和切碎的白甘蓝不同品种中李斯特菌增殖的数据，但关于这种病原体在红甘蓝上的命运尚无信息。因此，本研究旨在探索李斯特菌在不同温度下储存时对切割红甘蓝（芸薹属 oleracea L.var.capitata f.rubra）的存活情况。将红甘蓝切成 5 乘 4 厘米的块状并用六株利福平抗性李斯特菌鸡尾酒点接种，初始接种水平为 4 log CFU/g。将样品在 5 或 10°C 下储存 14 天或在 25°C 下储存 7 天。在储存过程中每隔一段时间，通过将甘蓝与 Butterfield 的磷酸盐缓冲液匀浆来计数李斯特菌，并用添加利福平的脑心浸液琼脂对连续稀释液进行平板计数。在 5°C 下储存时，切割的红甘蓝上未观察到李斯特菌的生长，仅在较高温度下观察到最小的增殖。在 10 和 25°C 下储存 3 天后，分别确定了 0.58 和 1.07 log CFU/g 的显著种群增加；然而，在 10°C 下也观察到从 3 天到 14 天的 0.77 log CFU/g 的显著减少。在 5 和 10°C 下储存的切割红甘蓝上李斯特菌的模型生长率分别为 0.11 ± 0.03 和 0.27 ± 0.07 log CFU/g/天，计算出的 1-log CFU/g 增加时间分别为 9.51 和 3.70 天；然而，在本研究中，在这两种温度下，李斯特菌都没有达到 1-log 增加。在 25°C 下，切割红甘蓝上李斯特菌的模型生长率为 1.15 ± 0.36 log CFU/g，导致计算出的和观察到的 1-log 增加分别为 0.87 和 3.00 天。本研究的结果有助于了解李斯特菌在不同温度下储存时在切割红甘蓝上的命运。
