Abstract
The effect of nisin-producing lactic acid bacteria on late butyric acid fermentation during cheese ripening was evaluated by making Gouda cheese without the addition of nitrate but with the combination of conventional LD type and nisin-producing lactic starters.
Control cheese, made with only the conventionail LD type starter, blew within 2 months of ripening, whereas the test cheese blew to an extent inversely proportional to its content of nisin. Butyric acid fermentation could be almost completely prevented in the presence of at least 50 IU/g of nisin.
Regarding proteolysis in cheese repening, the maturity and the non-protein nitrogen ratio of cheese were sometimes higher in the test cheeses than in the control, and no apparent delay in ripening was observed when nisin-producing starter was used. The development of unwanted (bitter and unclean) flavors occurred for some of the test cheeses, although flavor was assessed as being rather good for others. The use of nisin-producing starter did not appear to directly affect cheese flavor.
These findings suggest that the mixture of 1% conventional LD type starter and 0.5% to 1% nisin-producing starter, which is prepared by incubating a selected species of lactic acid bacteria in skim milk medium at 30℃ for 24 hrs, should be able, in the absence of nitrate, to prevent butyric acid fermentation in the late stage of cheese ripening without affecting the quality of cheese.
