The Growth and Survival of Streptococcus Faecalis in Pasteurized Milk American Cheddar Cheese

In a previous paper (1) it was shown that the addition of Streptococcus faecalis starter to pasteurized cheese milk increased the rate of ripenlug and improved the flavor of American Cheddar cheese.Such an effect naturally directed the attention of the authors to the growth characteristics of this organism in cheese.It is well known that the bacteria normally found in commercial lactic cheese starters do not survive for any great length of time in cheese.S. faecalis, on the other hand, is considered to be a rugged type of organism, able to survive and grow under conditions which would soon destroy many other types.As American Cheddar cheese in many respects affords conditions unfavorable for growth of most bacteria, it would be interesting to observe the degree of adaptation that S. faecalis could make in such an environment.That this organism commonly is found in cheese has been noted by several investigators.Sherman and Stark ( 5) found S. faecalis in 1-day-old Swiss cheese, while Foster et al. (2) fouud large numbers of these bacteria in ripening Brick cheese.Tittsler et al. (6) stated that enterococci were one of the predominant bacterial types in ripening Cheddar cheese made from pasteurized milk.Up to the present, very little study has been made of the course of growth and of the survival period of S. faecalis in Cheddar cheese.Data of this nature should aid in an understanding of the effect of this organism upon cheese flavor development as well as provide general informationwhich will be required as knowledge of the relationship of S. faecalis to foods becomes more apparent.A study covering the foregoing phases was conducted. EXPERIMENTAL METHODSMethods used consisted of the total plate count using standard tryptone-glucose-extract-skim milk agar, a selective medium plate count for enterococci, and conventional physiological identification tests for enterococci.The selective medium was that developed by White and Sherman (7) for the determination of enterococci in milk.It contains 0.5 per