Changes in protein fractions of milk obtained from cows with mastitis caused by Staphylococcus aureus. Preliminary studies

The effect was studied of cow udder infection with S. aureus on changes of milk proteins. The tested milk was derived from two cows of the black-white lowland breed aged 5 years in the second stage of lactation. Proteins soluble and insoluble at pH 4.6 were characterized by means of starch-urea and polyacrylamide gel electrophoresis. The solution of nitrogen compound reacting with ninhydrin and soluble at pH 4.6 was separated by gel filtration, thin-layer chromatography and high-voltage paper electrophoresis, thin-layer chromatography and high-voltage paper electrophoresis. In the milk of the infected cow degradation of alpha s, beta and kappa casein, and increased content of gamma immunoglobulin. In whey proteins a rise was observed of serum albumin content and a decrease of beta-lactoglobulin and alpha lactoalbumin. In the solution after precipitation of casein at pH 4.6 in the milk of the infected cow a greater number of fractions reacting with ninhydrin was found. The observed range of degradation changes in milk protein in the infected cow (S. aureus) suggests that it has a negative effect on the technological, nutritional and hygienic value of milk.