Del Torre M, Stecchini M L, Braconnier A, Peck M W
Institute of Food Research, Norwich Research Park, Colney, Norwich, NR4 7UA, UK.
Int J Food Microbiol. 2004 Nov 1;96(2):115-31. doi: 10.1016/j.ijfoodmicro.2004.01.004.
Sales and consumption of refrigerated processed foods of extended durability (REPFEDs) have increased many-fold in Europe over the last 10 years. The safety and quality of these convenient ready-to-eat foods relies on a combination of mild heat treatment and refrigerated storage, sometimes in combination with other hurdles such as mild preservative factors. The major hazard to the microbiological safety of these foods is Clostridium botulinum. This paper reports on the prevalence and behaviour of proteolytic C. botulinum and non-proteolytic C. botulinum in gnocchi, a potato-based REPFED of Italian origin. Attempts to isolate proteolytic C. botulinum and non-proteolytic C. botulinum from gnocchi and its ingredients were unsuccessful. Based on assessment of the adequacy of the methods used, it was estimated that for proteolytic C. botulinum there was < 25 spores/kg of gnocchi and < 70 spores/kg of ingredients. The total anaerobic microbial load of gnocchi and its ingredients was low, with an estimated 1 MPN/g in processed gnocchi. Most of the anaerobic flora was facultatively anaerobic. A few obligately anaerobic bacteria were isolated from gnocchi and its ingredients and belonged to different Clostridium species. The protection factor, number of decimal reductions in the probability of toxigenesis from a single spore, was determined for eight different gnocchi formulations by challenge test studies. For all gnocchi stored at 8 degrees C (as recommended by the manufacturer) or 12 degrees C (mild temperature abuse), growth and toxin production were not detected in 75 days. The protection factor was >4.2 for proteolytic C. botulinum, and >6.2 for non-proteolytic C. botulinum. When inoculated packs were stored at 20 degrees C (severe temperature abuse), toxin production in 75 days was prevented by the inclusion of 0.09% (w/w) sorbic acid (protection factors as above), however in the absence of sorbic acid the packs became toxic before the end of the intended shelf-life and the protection factors were lower. Providing sorbic acid (0.09% w/w) is included in the gnocchi, the safety margin would seem to be very large with respect to the foodborne botulism hazard.
在过去10年里，欧洲耐储存冷藏加工食品（REPFEDs）的销量和消费量增长了许多倍。这些即食方便食品的安全性和质量依赖于温和热处理与冷藏储存的结合，有时还会结合其他障碍因素，如温和的防腐因素。这些食品微生物安全的主要危害是肉毒梭菌。本文报道了在意大利原产的以土豆为基础的耐储存冷藏加工食品意大利面疙瘩中，蛋白水解性肉毒梭菌和非蛋白水解性肉毒梭菌的流行情况及特性。从意大利面疙瘩及其原料中分离蛋白水解性肉毒梭菌和非蛋白水解性肉毒梭菌的尝试未成功。基于对所用方法充分性的评估，估计对于蛋白水解性肉毒梭菌，每千克意大利面疙瘩中孢子数<25个，每千克原料中孢子数<70个。意大利面疙瘩及其原料的总厌氧微生物负荷较低，加工后的意大利面疙瘩中估计为每克1个MPN。大多数厌氧菌群为兼性厌氧。从意大利面疙瘩及其原料中分离出一些专性厌氧菌，它们属于不同的梭菌属。通过挑战试验研究，确定了八种不同意大利面疙瘩配方的保护因子，即单个孢子产毒概率的十进制减少数。对于所有在8℃（制造商推荐温度）或12℃（轻度温度滥用）储存的意大利面疙瘩，在75天内未检测到生长和毒素产生。对于蛋白水解性肉毒梭菌，保护因子>4.2，对于非蛋白水解性肉毒梭菌，保护因子>6.2。当接种的包装在20℃（严重温度滥用）储存时，通过添加0.09%（w/w）山梨酸（保护因子如上）可防止75天内产生毒素，然而在没有山梨酸的情况下，包装在预期保质期结束前就会产生毒素，且保护因子较低。如果意大利面疙瘩中含有山梨酸（0.09% w/w），那么相对于食源性肉毒中毒危害而言，安全系数似乎非常大。
