Survival characteristics of E. coli O157:H7, S. typhimurium and S. aureus during kefir fermentation

Abstract

In this research, the growth and survival of E. coli O157:H7, Salmonella typhimurium and Staphylococcus aureus were investigated during kefir fermentation. Two different levels of inoculation of the strains were conducted; the levels of 102 CFU/ml (EC-1, SA-1 and S-1) and 103 CFU/ml (EC-2, SA-2 and S-2). At 0, 2, 6, 12, and 24 hours of kefir fermentation at 23 ± 1°C, samples were taken and the counts of E. coli O157:H7, S. typhimurium, and S. aureus were determined. EC-1 grew from 2.29 ± 0.02 log CFU/ml to 4.13 ± 0.18 log CFU/ml whereas EC-2 grew from 3.22 ± 0.04 log CFU/ml to 6.78 ± 0.99 log CFU/ml. Both S-1 and S-2 viable populations grew during the fermentation period, where sample S-1 grew from 2.37 ± 0.20 log CFU/ml to 4.64 ± 0.67 log CFU/ml and sample S-2 grew from 3.52 ± 0.07 log CFU/ml to 5.60 ± 0.10 log CFU/ml. SA-2 strains grew from 3.06 log CFU/ml to 3.64 log CFU/ml, SA-1 strains grew from 2.28 log CFU/ml to 2.66 log CFU/ml. According to the findings, E. coli O157:H7, S. typhimurium, and S. aureus can survive in kefir during fermentation.