Abstract
The optimal levels of LD type and nisin-produucing lactic starters for cheese curd making were determined in order to evaluate the degree to which nisin-producing lactic acid bacteria prevents butyric acid fermentation in Gouda cheese.
Cheese curd making tests were repeated on a small scale with various contents of LD type and nisin-producing lactic starters, and the number of the latter bacteria and the production of nisin in cheese curd were determined. Nisin concentration in cheese curd was proportional to the number of nisin-producing lactic acid bacteria. To obtain nisin at concentrations above 100 IU/g after salting, at least 5.0×108 cfu/g nisin-producing lactic acid bacteria must be present in the curd.
When the ratio of nisin-producing starter to LD type starter was increased, nisin, which was transported via the starter culture and further produced by the nisin-producing starter bacteria, was found to suppress the growth of LD type lactic acid bacteria, and particularly that of nisin-sensitive Lactococcus lactis subsp. cremoris SC-3.
On the other hand, when the ratio of nisin-producing starter to LD type starter was reduced, the growth of nisin-producing lactic acid bacteria was inhibited by LD type starter bacteria, and the reduced numbers of nisin-producing lactic acid bacteria produced smaller amounts of nisin.
This study of cheese curd making tests showed that even with the addition of 0.5% nisin-producing starter, acid production remained almost normal during curd making.
