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Twenty-four different supplies of fresh Mozzarella cheese whey were pasteurized. Twenty-one were evaporated into seven condensed whey product (CWP) categories; three were not evaporated. Each whey and whey product was subsequently manufactured into Ricotta cheese. Average total solids (TS) content ranged from 6.70 to 35.90%. The Ricotta cheeses manufactured from five of the eight categories were judged to be acceptable for the market. Average TS (%) of the acceptable categories were 6.70, 10.31, 14.87, 18.02 and 20.86. Ricotta cheeses manufactured with CWP of average TS contents of 25.10, 28.67 and 35.90% were not acceptable. Flavor defects for Ricotta cheeses that were unacceptable included coarse, unnatural and unclean; body and texture defects included grainy and mealy. We recommend the manufacture of whey Ricotta cheese with approximately 21% CWP. Yield based on total weight for CWP with 20.86 TS averaged 21.32%, more than four times greater than the noncondensed whey. Ricotta cheese from CWP of 20.86% TS tested 69.75% moisture, 7.55% protein, 13.37% lactose, 4.30% fat and 0.72% salt. Large amounts of protein and lactose remained in the Ricotta cheese whey and must be handled properly to prevent pollution.

Two antifungal agents, pimaricin and mycostatin, added to Cottage cheese through the wash water at concentrations of 20, 50, or 100 mug/ml of wash water or added through the cheese dressing at 1, 2, or 5 mug/g retarded the growth of Aspergillus niger and Saccharomyces cerevisiae and improved the shelf-life of the cheese. In general, cheese with highest concentration of antifungal agent and stored at lowest temperature had best keeping quality. Pimaricin was slightly more effective than mycostatin in inhibiting fungi; inhibition was greater if the antifungal agents were added to the cheese dressing and the cheese was stored at low temperature; and A. niger was more sensitive to the inhibitors than S. Cerevisiae.

As bacterial numbers in raw milk increased to millions and pH decreased to 6.3 and lower, inhibitory substances were produced that gave positive tests by the Bacillus subtilis disc assay and Sarcina lutea cylinder plate method. These substances were inactivated by heat treatment. The inhibitor was not lactic acid. Results of our study emphasized that all laboratories that test raw milks for antibiotics must be certain to heat samples before reporting a positive test result for inhibitor. If a heat-sensitive inhibitor is found in raw milk, one should evaluate the quality control program.