Studies On Microscopic Determination Methods For SCC And Relationship Between SCC And Viscosity Of Chemical Denaturized Raw Milk

Somatic cell count (SCC) is a highly valuable reference index for raw milk quality control, food safety, mastitis test and cow raising level evaluation. In our country SCC limited has not been actually put in practice yet, and it just a matter of time. Some primary research work carried out for the inevitable trend, and some worthy data obtained:1. The result of a preliminary survey on SCC of individual cow milk sample reveals that the SCC level of the area are very high, it also implies the high incidence of intramammary infection of the region. SCC average (×10,000 cells/ml) and percentage above the SCC 500,000cells/ml the three sampling areas of the city were: 118.4 (n=108) and 50% over 500,000cells/ml for dairy farm of Inner Mongolia University; 230.5 (n=530) and 97.7% over 500,000cells/ml for samples from a suburban raw milk resources; 57.8 (n=100) and 31% over 500,000cells/ml for the retail milk samples from the urban. It was found that SCC of three period of milking is significantly different. SCC average of the terminal is 3.9 time higher and the beginning and 4.7 than middle period of each milking, it suggests that attention should be paid to representativeness of the sample when determining SCC of individual cow.2. Methylene blue staining is the preferable and the most accurate one among the tree available staining methods for SCC direct microscopy counting. Milk samples should be preserved at 4℃and detected within 48 hours; Somatic cells almost completely vanished after 12 hours storage at room temperature. Formaldehyde does not significantly protect and stabilize somatic cells shape and SCC values. Heating, freezing and homogenization significantly damage the somatic cells, and make the cytomorphometric methods can not obtain correct SCC.3. After denaturalized by chemical denaturant with surfactant as main ingredient, the viscosity of raw milk increased significantly, and the denaturalized viscosity has a linear correlation with the SCC (with R2 0.74 to 0.98 during 16 experiments). The range of viscosity of raw milk (average +2 SD) is 3.6±1.64 cP (n = 272); and 17.6±29.5cP (n = 272) for the viscosity of denaturalized raw milk, with the minimum 3.04 cP and the maximum 88.6cP.The ingredient of denaturants has decisive effect on the increase range of denaturized viscosity. Optimization of denaturant can achieve accurate regression between denaturized viscosity and SCC. Pasteurization, freezing and homogenization of milk have no impact on the regression between the denaturized viscosity and SCC. It is a unique advantage of the principle to determining SCC. The changes of casein, whey protein, fat and bacteria count have no influence on the mentioned correlation and regression too. Results also implied that the SCC above 1000,000 cells/ml can be accurately determined the regression model, and may not for the SCC below the number.