EFFECTS OF MILK SOMATIC-CELL COUNT ON COTTAGE CHEESE YIELD AND QUALITY

Eight Holstein cows in midlactation were selected for low milk somatic cell count (SCC) and the absence of the pathogens that cause mastitis . Milk collection and cottage cheese manufacture from low SCC milk wer e replicated on each of 4 d (control period). Each cow was infused wit h 1000 cfu of Streptococcus agalactiae. One week after infusion, milk fr the same eight cows was collected and commingled. On each of 4 d, c ottage cheese was made from milk with high SCC (treatment period). A m ass-balance protocol, accounting for protein and total solids, was use d to determine recoveries in whey, wash water, and uncreamed curd. Act ual yields, yields adjusted for composition, and theoretical yields of uncreamed curd were calculated. Mean milk SCC for the periods with th e low SCC (control) and the high SCC (treatment) were 83 x 10(3) and 8 72 x 10(3) cells/ml, respectively. The recovery of protein in the uncr eamed curd was higher during the low SCC period than during the high S CC period (75.85% vs. 74.35%). High SCC and the associated higher prot eolytic activity caused higher protein loss in the whey and wash water and more curd fines. The percentage of total solids recovery in uncre amed curd was higher for high SCC milk because the lactose content of the high SCC milk was 0.27% lower than that of the low SCC milk. The m oisture content of the curd was higher for the high SCC milk (82.75% v s. 83.81%). Proteolysis during refrigerated storage was faster in cott age cheese made from high SCC milk. The yield efficiency of uncreamed curd, adjusted for composition based on 81% moisture, was 4.34% lower for the cottage cheese curd made from high SCC milk.