Factors Influencing Acid Production by Cheese Cultures. II. Influence of Bacteriophage on Acid Production in the Manufacture of Cheddar and Cottage Cheese

Abstract

Summary Slow acid production, due to the presence of bacteriophage, in the manufacture of cheddar cheese usually was apparent at the time of draining the whey or shortly thereafter. The presence of bacteriophage resulted in almost complete cessation of acid production in the manufacture of cheddar cheese when either single-strain or multiple-strain cheese cultures were employed. Cheddaring for a long period of time (4 or 5 hrs.) did not result in an appreciable increase in acidity when acid production was slow because of bacteriophage action. The presence of bacteriophage in bacteria-free nitrates of whey, culture, etc., could be demonstrated by adding a small amount of the filtrate to pure cultures of S. lactis isolated from the culture used in the manufacturing process and also by the production of bacteriophage plaques on a solid medium. When a vat of skim milk intended for cottage cheese was contaminated slightly with bacteriophage active against the culture employed, acid formation was very slow for about 24 hrs. after setting. During this same period the bacteria count showed a slight increase, then a large decrease, and finally a large increase. The bacteriophage titer increased for 7 to 12 hrs. following setting and then remained practically constant. When secondary growth occurred (usually after 24 hrs.), acid production proceeded normally.