Faculty of Biology, University of Latvia, Blvd. Kronvalda 4, Riga, LV-1586, Latvia.
Int J Food Microbiol. 2010 Dec 15;144(2):317-21. doi: 10.1016/j.ijfoodmicro.2010.10.001. Epub 2010 Oct 8.
In this study, a microbiological challenge test in three artificially contaminated retail mixed mayonnaise-based ready-to-eat salads stored at refrigerator temperatures (3°C and 7°C) for 48h was carried out. Shrimp-tomato salad, smoked ham salad and garlic cheese salad were separately contaminated by a suspension of particular Listeria monocytogenes strains. The number of L. monocytogenes, Enterobacteriaceae, staphylococci and total plate count (CFU/g) was determined. Listeria monocytogenes growth potential in the salads was calculated and evaluated. A significant increase in total plate count and L. monocytogenes count throughout storage of all three investigated salads was found. Enterobacteriaceae levels were high at the beginning in all salads but significantly (p<0.05) decreased throughout the experiment depending on the temperature. All investigated L. monocytogenes strains demonstrated growth at both temperatures but expressed different growth potential. Especially garlic cheese salad and smoked ham salad were able to support the growth of Listeria. Shrimp-tomato salad supported growth the least. The growth potential increased with the increasing temperature and exceeded 0.5 log(10) CFU/g in many cases. If the potential for growth is >0.5 log(10) CFU/g, food products can potentially endanger human health. Reference strain (ATCC 7644) showed the least growth potential almost in all cases in comparison with strains isolated from frozen pollock loins and from thermally treated specialty sausage containing preservatives. To eliminate the occurrence of microbiological risks, the shelf-life of the studied salads was estimated.
本研究对三种人工污染的零售混合即食蛋黄酱沙拉进行了微生物挑战性试验，这些沙拉在 3°C 和 7°C 的冰箱温度下储存 48 小时。虾番茄沙拉、熏火腿沙拉和大蒜奶酪沙拉分别被特定的单增李斯特菌菌株的悬浮液污染。测定了单增李斯特菌、肠杆菌科、葡萄球菌和总平板计数（CFU/g）的数量。计算和评估了沙拉中单增李斯特菌的生长潜力。在所有三种研究沙拉的整个储存过程中，总平板计数和单增李斯特菌计数均显著增加。在所有沙拉中，肠杆菌科水平在开始时都很高，但随着实验的进行，根据温度的不同，其数量显著（p<0.05）下降。所有研究的单增李斯特菌菌株在两种温度下均表现出生长，但表现出不同的生长潜力。特别是大蒜奶酪沙拉和熏火腿沙拉能够支持李斯特菌的生长。虾番茄沙拉的支持生长能力最低。随着温度的升高，生长潜力增加，在许多情况下超过 0.5 log(10) CFU/g。如果生长潜力>0.5 log(10) CFU/g，则食品可能对人类健康构成潜在威胁。参考菌株（ATCC 7644）与从冷冻鳕鱼排和含防腐剂的热处理特色香肠中分离出的菌株相比，在几乎所有情况下表现出的生长潜力最小。为了消除微生物风险的发生，估计了研究沙拉的保质期。
