Antibacterial activity and antioxidant capacity of dairy kefir beverages

Kefir traditionally is based on pasteurised milk and the use of other substrates is unusual. Kefir beverages made with raw milk (RMK), pasteurised milk (PMK) or whey (WK), were obtained and fractionated in microbial cells and supernatants. Antioxidant and antibacterial activity of fractions against Cronobacter sakazakii and Escherichia coli were analysed. The highest antioxidant activity was obtained for PMK with values between 8500 and 10 000 μm TE/mg. Microbial extracts from RMK and PMK showed a reduction of C. sakazakii of 7 log units; while microbial extracts and supernatants from RMK decreased E. coli in 3 and 5 log units, respectively. These results indicate that dairy kefir beverages can be an excellent source of defensive agents to fight against bacteria that cause gastrointestinal disorders.