Evaluation of Survival of Salmonella Typhimurium in Homemade Kefir

Abstract

Kefir is a fermented probiotic dairy product which is fondly consumed with its peculiar, pleasant taste. However, like all dairy products, kefir may also constitute a risk for pathogenic microorganisms, which is particularly associated with its relatively long fermentation period that requires numerous processing steps. The objective of this study was to investigate the putative growth and risk status of Salmonella during the production and shelf life of kefir. For this purpose, kefir samples prepared with Salmonella reference culture-spiked milk, were divided into two groups; one was fermented at cold temperatures while the other was left to fermentation at ambient temperature. Salmonella enumeration and pH measurements of each group was performed at every 24 hours for six days. According to data obtained, Salmonella count has increased to 5.60 log cfu/ml on the first day of incubation at ambient temperature, which then started to decrease with ongoing fermentation. However, the bacteria was still present at the 6th day. Bacterial count of refrigerated kefir did not exhibit a sudden logarithmic rise, reaching its highest value at 2.87 log cfu/ml level and did not reveal a marked drop in comparison to the initial count, which instead sustained at 1.98 log cfu/ml level and thus bacteria survived until the end of the determined shelf life.