Jacobsen Tomas, Koch Anette Granly
Danish Meat Research Institute, DK-4000 Roskilde, Denmark.
J Food Prot. 2006 Mar;69(3):532-41. doi: 10.4315/0362-028x-69.3.532.
The aim of this study was to determine the effect of history of inoculum and preservatives on the lag phase and growth rate of Listeria monocytogenes strains in meat products packaged under modified atmosphere conditions. Inocula with different histories were added to meat models, and growth rate and lag phase of two strains of L. monocytogenes were measured at 5 and 10 degrees C. The meat model stored at 10 degrees C contained sodium lactate, but the model stored at 5 degrees C did not. The five different histories of the inocula included cold propagation, biofilm formation, and starvation. The lag phase ranged from 1 to 10 days and was affected by the history of the inoculum, whereas the growth rate was constant except for one combination of history of inoculum and strain, where growth did not start during the incubation period. In a second series of experiments, the growth rate and lag phase of the two Listeria strains and the effects of two different histories of inoculum were tested in meat models with pH 5.7 or 6.5 and increasing amounts of NaCl. The growth rate depended on salt concentration, bacterial strain, and pH, whereas lag phase duration depended on history of inoculum, salt concentration, and pH. The lag phase duration was highly dependent on the history of the inoculum, and higher amounts of preservative (NaCl) made these effects even more noticeable. The results of this study underline the importance of the effects of the history of the inoculum on lag phase duration and could be used to predict lag phase in industrial meat products.
本研究的目的是确定接种物和防腐剂的历史对在气调包装条件下肉类产品中单核细胞增生李斯特菌菌株的延迟期和生长速率的影响。将具有不同历史的接种物添加到肉类模型中，并在5℃和10℃下测量两株单核细胞增生李斯特菌的生长速率和延迟期。储存在10℃的肉类模型含有乳酸钠，但储存在5℃的模型则没有。接种物的五种不同历史包括冷传代、生物膜形成和饥饿。延迟期为1至10天，受接种物历史的影响，而生长速率除了一种接种物历史和菌株的组合外是恒定的，在该组合中培养期间没有开始生长。在第二系列实验中，在pH值为5.7或6.5且NaCl含量增加的肉类模型中测试了两株李斯特菌菌株的生长速率和延迟期以及两种不同接种物历史的影响。生长速率取决于盐浓度、细菌菌株和pH值，而延迟期持续时间取决于接种物历史、盐浓度和pH值。延迟期持续时间高度依赖于接种物历史，并且较高含量的防腐剂（NaCl）使这些影响更加明显。本研究结果强调了接种物历史对延迟期持续时间影响的重要性，可用于预测工业肉类产品中的延迟期。
