A study on the role of the indigenous microflora of raw milk on the ripening of Cheddar cheese

Antibiotics (500 U Nisin, 12 U Penicillin G and 12μg Streptomycin g^-1 curd) were added at salting to Cheddar cheese curd made from raw or pasteurised milk to inhibit the growth of non-starter lactic acid bacteria (NSLAB) in order to study their significance in cheese ripening. The antibiotics used inhibited the growth of NSLAB in cheese made from pasteurised milk for 1 month and reduced their growth thereafter up to 3 months. Antibiotics also reduced the growth of NSLAB in the raw milk cheeses up to 2 months. The level of water-soluble N showed no differences between the cheeses. Differences in peptide profiles were observed between cheeses made from raw or pasteurised milk, and between cheeses treated with antibiotics and their controls. Cheeses treated with antibiotics had higher concentrations of free amino acids than their controls. Off-flavours developed in both raw milk cheeses which were awarded lower grading scores than the pasteurised milk cheeses at most stages during ripening. The results of this study show that the antibiotics used were capable of inhibiting NSLAB, particularly in cheeses made from pasteurised milk and that NSLAB influenced the flavour and biochemistry of Cheddar cheese.