QUALITY AND YIELD OF COTTAGE CHEESE INFLUENCED BY PSYCHROTROPHIC MICROORGANISMS IN MILK

Pasteurized milk, milk treated with H2O2-catalase and raw low-protein milk inoculated with each of 2 psychrotrophic organisms and uninoculated (control) milks were made into cottage cheese by the direct-acid-set method. Combinations of raw milk treatment, psychrotrophic concentration, separation temperature and control were studied along with peroxide-catalase treated milk and pasteurized milk similarly inoculated and separated. Also, 1 trial with pasteurized milk similarly inoculated and separation was made by the culture method and studied. Later, raw and peroxide-catalase treated milks were inoculated after separation instead of before separation prior to being made into cottage cheese by the direct-acid-set method. Vat failures occurred only when milk was inoculated with the psychrotrophic bacteria before separation. The higher the separation temperature and count, the greater was the tendency for vat failures. When psychrotrophic bacteria were more numerous in cheese milk, yields were lower than in uninoculated milk whether inoculation was before or after separation. Proteolysis was greater in milk inoculated before separation when vats failed than when failures did not occur. When inoculation was after separation and much proteolysis, no vats failed. The combination of proteolysis and higher separation temperatures apparently contribute to vat failure in cottage cheese making.