Abstract
This study determined the composition, somatic cell count (SCC) and relative percentage of α-S1, α-S2, β and κ caseins in ethanol-unstable (UNA) and stable bulk milk samples. The sampling plan involved farms that supplied milk to one dairy plant located in the northeast region of Sao Paulo, Brazil, in May (fall), July (winter), and September (spring) 2007. Three hundred thirty-four bulk milk samples within an acceptable range of pH and acidity were included in the study and divided into two groups: a) stable milk, when protein precipitation only occurred with 78% ethanol (v/v); and b) unstable (UNA) milk, when the precipitation occurred with 72% ethanol (v/v). From the total samples analyzed, 77 (23%) were unstable in the 72% ethanol (v/v), although they have shown normal pH and acidity, and 41 (12.3%) were stable in 78% ethanol (v/v). No differences were found between relative percentages of α and β- casein in UNA or stable milks. However, UNA samples showed higher SCC, as well as lower casein and lactose contents. Results indicated that the high SCC may be involved as a causal factor for the high incidence of UNA milks in the herds studied.
Highlights
Milk ethanol stability is defined as the minimum concentration of added aqueous ethanol that causes milk coagulation (HORNE; PARKER, 1979)
Ethanol stability is considered a simple, reliable test for detecting milk of poor microbiological quality, falsepositive results in milks with normal pH have been reported in Brazil, mainly in the southern states of the country (ZANELA et al, 2009)
Three hundred thirty-four bulk milk samples were collected from farms that supplied milk to a dairy plant located in the northeast of the State of São Paulo, Brazil
Summary
Milk ethanol stability is defined as the minimum concentration of added aqueous ethanol that causes milk coagulation (HORNE; PARKER, 1979). This test is used worldwide in reception platforms of dairy plants to predict heat stability of raw milk (CHAVEZ et al, 2004). In Brazil, the Ministry of Agriculture recommends the use of 68-72% (v/v) ethanol in the ethanol stability test (BRASIL, 1981). Several dairy factories employ even higher ethanol concentrations, especially manufacturers of ultra-high temperature milk. Ethanol stability is considered a simple, reliable test for detecting milk of poor microbiological quality, falsepositive results in milks with normal pH have been reported in Brazil, mainly in the southern states of the country (ZANELA et al, 2009)
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