Fruitiness, caused by growth of Pseudomonas fragi, was the defect that most commonly limited the storage life of commercial cottage cheese. Cultures of Pseudomonas fragi, Pseudomonas viscosa, and Alcaligenes metalcaligenes produced typical defects in cottage cheese at initial pH values as low as 4.6 and at temperatures as low as 3.5° C. Low temperature was very effective as a means of retarding the development of defects. Of the species studied, P. fragi was retarded least by low temperature. Violet red bile agar was found satisfactory for enumeration of the three species of bacteria.
Dr. Edwin B. Collins was graduated in 1943 from Clemson College of South Carolina with a B.S. in Dairying. Upon return from service in the U.S. Army, he completed his M.S. and Ph.D. degrees in Dairy Bacteriology at Iowa State College in 1948 and 1949, respectively. He is now Assistant Professor of Dairy Industry and Assistant Dairy Bacteriologist in the Experiment Station, University of California, Davis.