Effect of different concentrations of nisin on starter culture of model Cheeses manufactured from ultrafiltrated milk

Nisin is a natural preservative produced by strains of Lactococcuslactis subsp. Lactis, has been approved for use in food by the Joint Food and Agricultural Organization/World Health Organization (FAO/WHO) Committee on Food Additives and has been awarded generally recognized assafe (GRAS). It remains the only bacteriocin allowed in food as an addedpreservative. Nisin has a broadspectrum of antimicrobial activity againstgram-positive bacteria, thus one of the problems associated with nisinapplication is inhibition of starter culture and prevention of ripening, which is required for development of cheese characteristics during ripening. In the current study, the effects of different concentrations of nisin and temperature on growth and activity of lactic acid bacteria in model cheeses manufactured fromultrafiltrated milk was evaluated. Cheese samples were supplemented with nisin atconcentrations of 0, 2, 4 and 6 μg/g and stored at 8 and 25 °C up to 60 days. Microbiological and physico chemical properties of the cheese samples were analyzedat 0, 1, 8, 15, 30, 45 and 60 days. Results showed that addition of nisin at concentrations of 4 and 6 μg/g affects (p<0.01) the growth of lactic acid bacteria and so prevents pH reductionduring cheese ripening (p<0.01). Moreover, roomtemperature decreased significantly (p<0.01)nisin activity. According to the results, nisin at concentrations less than 4 μg/g along with refrigeratorstorage temperature could be used as a natural preservative in Cheese manufactured fromultrafiltered milk.