Growth of Listeria monocytogenes and Clostridium sporogenes in Cottage Cheese in Modified Atmosphere Packaging

Abstract

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°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°C. Clostridium sporogenes failed to grow under any condition applied in this study. In the conventionally packaged cottage cheese, L. monocytogenes increased from 104 to 107 cfu/g after lag phases of 28 and 7 d at 4 and 7°C, respectively. In contrast, L. monocytogenes failed to grow in cottage cheese packaged with CO2 and stored at 4°C up to 63 d and increased from 104 to 105 cfu/g in products packaged with CO2 at 7°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. © 1993, American Dairy Science Association. All rights reserved.