HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kosikowsky, F. V. Articles by Dahlberg, A. C. Search for Related Content PubMed Articles by Kosikowsky, F. V. Articles by Dahlberg, A. C.

The Growth and Survival of Streptococcus Faecalis in Pasteurized Milk American Cheddar Cheese¹

Department of Dairy Industry, Cornell University, Ithaca, New York

ABSTRACT

Three lots of milk pasteurized at 143–145° F. for 30 minutes were made into American Cheddar cheese. These lots contained, respectively, 2 per cent commercial lactic starter, 1 per cent commercial lactic starter plus 1 per cent Streptococcus faecalis starter, and 2 per cent S. faecalis starter. A selective penicillin-azide medium was used to count and isolate the enterococci.

In 1-day-old cheese made with commercial lactic starter, the number of bacteria growing on the selective medium was small, 300 per ml., but these gradually increased to 23 million per ml. at the end of 120 days at 50° F., and to 28 million per ml. after 120 days at 60° F. At the end of 180 days the counts on the selective medium had decreased to 11 million and 13 million per ml. at 50 and 60° F., respectively. In this cheese most of the increase was due to lactobacilli and not to enterococci;

When S. faecalis was used as a starter for pasteurized milk American Cheddar cheese, the highest enteroeoccus count was found to exist in the cheese curds just prior to salting, the count being 500 million per g. for cheese containing 1 per cent commercial lactic starter plus 1 per cent S. faecalis starter, and 1,370 million per g. for the cheese containing 2 per cent S. faecalis starter.

S. faecalis was able to grow and survive in Cheddar cheese in large numbers for a considerable period of time, both at 50 and 60° F. At 50° F., cheese made with both lactic and S. faecalis starters still gave counts of 345 million per g., and cheese made with S. faecalis starter gave counts of 1,085 million per g. at the end of 60 days, whereas at 60° F. the former cheese contained 305 million per g. and the latter cheese contained 750 million per g. at the end of 60 days. At the end of 180 days the numbers of bacteria in the cheese growing on the selective medium had decreased, although considerable numbers still were present.

¹ This investigation was aided by a grant from the National Cheesa Institute. The authors are indebted to Mrs. Lois Phelps and Miss Catherine Verwoert for making many of the chemical analyses.