Antibacterial activity of Enterococcus faecium derived from Koopeh cheese against Listeria monocytogenes in probiotic ultra-filtrated cheese.

Viability of probiotic bacteria in food during maintenance and time of consuming in food has become a challenge in food hygiene and technology and is important for representing their beneficial health effects. The aim of this study was to determine the survival of probiotic Enterococcus faecium derived from Koopeh cheese added to industrial Iranian ultra-filtrated (UF) cheese and screening for antimicrobial activity of Enterococcus faecium against Listeria monocytogenes during two months of cheese ripening. Physiochemical and standard microbial methods were used for isolation of Enterococcus strains in cheese samples. The initial number of lactic acid bacteria (LAB) as starter culture was 6 Log g(-1) in control samples. The counts started to decrease slightly after day seven (p < 0.05) and dropped to 5 Log g(-1) at the end of 60 days. The count of LAB in the test groups decreased to 11 Log g(-1) on the day 60 of ripening. The number of Enterococcus faecium was 6 Log g(-1) on the day 60. The count of Listeria monocytogenes after 60 days of ripening in blank sample decreased 1 Log but in test samples with protective strain decreased 3 Log in 30 days and reached to zero at 45 days. There were not significant (p < 0.05) changes in chemical parameters such as fat, protein and total solid of UF cheese treatment groups. The results showed that Enterococcus faecium of Koopeh cheese was suitable for development of an acceptable probiotic UF cheese and could be adapted to industrial production of UF cheese.