The Nutritional Requirements of Lactic Streptococci Isolated from Starter Cultures. III. Variation in Growth-Promoting Properties of Fresh Whole Milks

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Abstract
Individual cow samples of milk exhibited variation in peptide content which was correlated with rate of acid production therein by certain mixed strain commercial and single strain lactic streptococcus starter cultures. Peptide content appeared to exert greater effect on rate of growth of lactic streptococci than the protein content of milk. When peptide levels were equivalent, no significant difference in initial rate of acid production occurred between Jersey and Holstein milk from which the fat was removed. Correlation between rate of growth and peptide content was poor in a number of samples of milk from mastitic animals and those in early or late stages of lactation.