Influence of raw milk quality on casein fractions in UHT processed milk

The effect of somatic cell count (SCC) and total bacterial count (TBC) in raw milk on casein fractions in UHT processed milk by indirect heating was investigated. Before UHT treatment, bulk tank raw milk was categorized into groups according to SCC and TBC. To study the effect of SCC, four groups of raw milk were selected: Group A (<100,000 cells mL -1 ), Group B (100,000-400,000 cells mL -1 ), Group C (400,000-800,000 cells mL -1 ) and Group D (800,000-1,200,000 cells mL -1 ). All groups had a low TBC (<100,000 cfu mL -1 ). To study the effect of TBC, two groups of raw milk were selected: Low TBC (<100,000 cfu mL -1 ) and high TBC (1-2 million cfu mL -1 ). The SCC of both groups was less than 100,000 cells mL -1 . UHT-processed milk prepared from each group was analyzed for casein fractions through Reversed-Phase HPLC. Somatic cell count and TBC in raw milk increased the proteolysis of UHT processed milk. High SCC caused a decrease (P<0.05) in the concentrations of the as- and β-casein, while high TBC caused a decrease (P<0.05) in K -, β- and α s -casein. An increase (P<0.05) in the γ-casein concentration was observed for milk with either a high SCC or a high TBC.