Helmond Mariette, Nierop Groot Masja N, van Bokhorst-van de Veen Hermien
Wageningen Food and Biobased Research, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
Wageningen Food and Biobased Research, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
Int J Food Microbiol. 2017 Jul 3;252:35-41. doi: 10.1016/j.ijfoodmicro.2017.04.008. Epub 2017 Apr 20.
Food spoilage is often caused by microorganisms. The predominant spoilage microorganisms of pasteurized, chilled ready-to-eat (RTE) mixed rice-vegetable meals stored at 7°C were isolated and determined as Paenibacillus species. These sporeforming psychrotrophic bacteria are well adapted to grow in the starch-rich environment of pasteurized and chilled meals. Growth of the Paenibacillus isolates appeared to be delayed by decreased (<7°C) temperature or chilled temperature (7°C) combined with decreased pH (<5), increased sodium chloride (>5.5%, corresponding with an a<0.934), or decreased a (<0.931; using sucrose). To gain insight in the effect of the pasteurization processing of the meal on spore inactivation, heat-inactivation kinetics were determined and D-values were calculated. According to these kinetics, pasteurization up to 90°C, necessary for inactivation of vegetative spoilage microorganisms and pathogens, does not significantly contribute to the inactivation of Paenibacillus spores in the meals. Furthermore, outgrowth of pasteurized spores was determined in the mixed rice-vegetable meal at several temperatures; P. terrae FBR-61 and P. pabuli FBR-75 isolates did not substantially increase in numbers during storage at 2°C, but had a significant increase within a month of storage at 4°C or within several days at 22°C. Overall, this work shows the importance of Paenibacillus species as spoilage microorganisms of pasteurized, chilled RTE meals and that the meals' matrix, processing conditions, and storage temperature are important hurdles to control microbial meal spoilage.
食物腐败通常是由微生物引起的。对储存于7°C的巴氏杀菌冷藏即食（RTE）米菜混合餐的主要腐败微生物进行了分离，并确定为芽孢杆菌属。这些形成芽孢的嗜冷菌非常适合在巴氏杀菌和冷藏餐的富含淀粉的环境中生长。芽孢杆菌分离株的生长似乎会因温度降低（<7°C）或冷藏温度（7°C）与pH值降低（<5）、氯化钠增加（>5.5%，对应aw<0.934）或aw降低（<0.931；使用蔗糖）相结合而延迟。为了深入了解餐食的巴氏杀菌处理对芽孢灭活的影响，测定了热灭活动力学并计算了D值。根据这些动力学，对于灭活营养型腐败微生物和病原体而言，高达90°C的巴氏杀菌对餐食中芽孢杆菌芽孢的灭活没有显著作用。此外，还测定了在几个温度下巴氏杀菌芽孢在米菜混合餐中的萌发情况；地芽孢杆菌FBR - 61和巴氏芽孢杆菌FBR - 75分离株在2°C储存期间数量没有大幅增加，但在4°C储存一个月内或22°C储存几天内数量显著增加。总体而言，这项工作表明芽孢杆菌属作为巴氏杀菌冷藏即食餐的腐败微生物的重要性，并且餐食的基质、加工条件和储存温度是控制微生物导致餐食腐败的重要障碍。
