Effects Of Raw Milk With Different Levels Of Somatic Cell Counts On The Quality Of Cheddar Cheese

In order to provide theoretical foundation for controlling SCC in raw milk during making cheese, the effect of SCC in raw milk on the quality a during ripening was studied.The milk used for making cheddar cheese was divided in three trials. Each trial had different SCC in milk(LSCC.56,000, MSCC.48,800, HSCC.476,1000). During ripening, proteolysis, lipolysis, titration acidity, the number of lactic acid bacteria, free calcium to total calcium, free phosphorus to total phosphorus, rheology, organoleptic evalution of all three cheeses were analyzed.The result are:1. The relationship between increasing milk scc and decreasing actual cheese yield is linear, and there is significant difference among three cheeses(p<0.05).2. There is a linear relationship between water soluble nitrogen (WSN): total nitrogen ratio of cheese and scc (p<0.01)before 180d of ripening, correlation coefficients(R) is 0.4261. Non-protein nitrogen (NPN): total nitrogen ratio of cheese correlated to scc(p<0.05) between 30d and 180d of ripening. The result of Urea-PAGE shows there is difference in proteolysis products of caseins among three cheeses.3. The content of free fatty acid of cheese of HSCC was significant higher than that of cheese of MSCC and LSCC(p<0.05)during ripening, and the content of free fatty acid of cheese positively correlated to scc(p<0.0001), R is 0.7579.4. Titration acidity of cheese positively correlated to scc (p<0.01)during ripening, R is 0.4938.5. The number of lactic acid bacteria increased markedly between 15 and 30 d of ripening. The relationship between increasing milk scc and decreasing number of lactic acid bacteria is linear, and there is significant difference among three cheeses(p<0.05).6. During ripening, free calcium to total calcium raised at first, then became stable later. free phosphorus to total phosphorus declined at first, then became stable later.7. Hardness and shearing force negatively correlated to scc ((p<0.01)during ripening, R is 0.5482 and 1.3977. Organoleptic evaluation shows there is sour flavor in the HSCC cheeses and it's texture is softer and viscid.The present investigation has shown the they quality and yield of LSCC cheddar cheese was better than cheese made from HSCC milk.