Chen J H, Hotchkiss J H
Institute of Food Science, Cornell University, Ithaca, NY 14853.
J Dairy Sci. 1993 Apr;76(4):972-7. doi: 10.3168/jds.S0022-0302(93)77424-X.
Low fat cottage cheese (pH 5.14) was inoculated with three strains of Listeria monocytogenes, serotypes 1a and 4b, an isolate from a dairy processing plant, and Clostridium sporogenes ATCC 3584. The cheese was packaged with or without added dissolved CO2 in polystyrene tubs overwrapped with or without high barrier heat shrink film and stored at 4, 7, and 21 degrees C for up to 63 d. The concentration of CO2 in the container headspace was 35% (vol/vol). The CO2 concentration in that headspace declined by one-third over the 63 d of storage at 4 degrees C. Clostridium sporogenes failed to grow under any condition applied in this study. In the conventionally packaged cottage cheese, L. monocytogenes increased from 10(4) to 10(7) cfu/g after lag phases of 28 and 7 d at 4 and 7 degrees C, respectively. In contrast, L. monocytogenes failed to grow in cottage cheese packaged with CO2 and stored at 4 degrees C up to 63 d and increased from 10(4) to 10(5) cfu/g in products packaged with CO2 at 7 degrees C. These data suggest that the addition of CO2 to cottage cheese to extend shelf-life does not represent an increased Listeria or botulism hazard but that cottage cheese could be a vehicle for listeriosis.
低脂农家干酪（pH 5.14）接种了三种单核细胞增生李斯特菌菌株，血清型分别为1a和4b、一株来自乳制品加工厂的分离株以及生孢梭菌ATCC 3584。将干酪包装在聚苯乙烯桶中，添加或不添加溶解的二氧化碳，桶外包裹或不包裹高阻隔热收缩膜，并在4℃、7℃和21℃下储存长达63天。容器顶部空间的二氧化碳浓度为35%（体积/体积）。在4℃储存63天期间，顶部空间的二氧化碳浓度下降了三分之一。在本研究采用的任何条件下，生孢梭菌均未生长。在传统包装的农家干酪中，单核细胞增生李斯特菌在4℃和7℃下分别经过28天和7天的滞后期后，从10⁴cfu/g增加到10⁷cfu/g。相比之下，在包装有二氧化碳并在4℃下储存长达63天的农家干酪中，单核细胞增生李斯特菌未能生长；在7℃下包装有二氧化碳的产品中，单核细胞增生李斯特菌从10⁴cfu/g增加到10⁵cfu/g。这些数据表明，向农家干酪中添加二氧化碳以延长保质期不会增加李斯特菌或肉毒中毒的风险，但农家干酪可能是李斯特菌病的传播媒介。
