EVALUATION OF A PHAGE-INHIBITORY MEDIUM FOR LACTOCOCCUS STARTERS IN PILOT CHEESE MANUFACTURE

Antiphage medium MAB18 was designed to inhibit phage multiplication in Lactococcus cells during propagation steps for cheesemaking. This med ium has the essential nutrients that allow bacterial growth, and polyp hosphates as internal pH control and as Ca2+ sequestrant. In the pilot experiments it was used in a mixed starter L. lactis subsp. cremoris and L. lactis subsp. lactis and its specific phage phi IL25. Lactic ac id production was higher and the pH lower when cells were grown in MAB 18 than in milk, while the number of initial added phages did not incr ease. Using starter prepared in the artificial medium, the yield of '' Minas Frescal'' cheese with and without phages was higher than that ob tained with starters grown in milk. The number of phages remained low during propagation in the medium and also in whey and cheese. Accordin g to physico-chemical characteristics and sensory evaluation, the chee ses produced using MAB18 were well accepted and within the standards o f this typical cheese. (C) 1996 Elsevier Science Limited