Fates of Salmonella Enteritidis and Cronobacter sakazakii in various multiple-strain yogurts and kefir during cold storage

Abstract

Many multiple-strain fermented milks such as yogurt and kefir have been developed and consumed to improve their nutritional and functional benefits. Since these fermented milks can be a vehicle of foodborne illness, we investigated the fates of Salmonella Enteritidis and Cronobacter sakazakii in four fermented milks: multiple-lactic acid bacteria (multi-LAB) yogurt, multiple-LAB-Bifidobacterium (multi-LAB-BIF) yogurt, pH 4.5 kefir (mild kefir), and pH 3.6 kefir (strong kefir). Each was inoculated with 5.6 and 5.8 log cfu/ml of S. Enteritidis and C. sakazakii, respectively, and stored at 4°C for 5 days. Strong and mild kefirs exhibited more potent antimicrobial activities than multi-LAB and multi-LAB-BIF yogurts, inactivating all viable pathogenic bacteria within 1 and 5 days, respectively. Despite having lower pH values than mild kefir (pH 4.49), multi-LAB (pH 4.25) and multi-LAB-BIF (pH 4.38) yogurts failed to clear viable S. Enteritidis cells in 5 days (> 5 log cfu/ml cells survived).