Consiglio Nazionale delle Ricerche (CNR), Istituto di Scienze dell'Alimentazione, Avellino, Italy.
J Agric Food Chem. 2012 Aug 15;60(32):8044-50. doi: 10.1021/jf3024563. Epub 2012 Jul 31.
A clear picture of the protein rearrangement in milk following UHT-treatment was drawn by a comparative analysis of the pH 4.6 soluble protein fraction (SPF) and the pH 4.6 insoluble protein fraction (IPF) recovered from raw and UHT-treated milk samples. The two protein fractions were analyzed by mono- or bidimensional gel electrophoresis under reducing and nonreducing conditions, and protein bands were identified by specific immunostaining. Results showed that bovine serum albumin, β-lactoglobulin, and, to a lesser extent, α-lactalbumin coprecipitated with caseins in UHT-treated milk samples at pH 4.6. These proteins were almost exclusively involved in high molecular weight aggregates held together by disulfide bonds. Partition of α-lactalbumin and bovine serum albumin in the protein fractions obtained upon acidification of milk at pH 4.6 was evaluated by competitive immunoassays. The ELISA-based results suggested the possibility of using pH 4.6 insoluble α-lactalbumin and bovine serum albumin, in addition to pH 4.6 insoluble β-lactoglobulin, as indicators of the intensity of the heat treatment applied to milk.
通过对比分析从生乳和超高温处理乳样中回收的 pH4.6 可溶性蛋白（SPF）和 pH4.6 不溶性蛋白（IPF），描绘了 UHT 处理后乳中蛋白重排的清晰图像。在还原和非还原条件下，采用单维或二维凝胶电泳对这两种蛋白进行分析，并通过特异性免疫染色鉴定蛋白条带。结果表明，在 pH4.6 时，牛血清白蛋白、β-乳球蛋白，以及在较小程度上的α-乳白蛋白与乳清蛋白共沉淀于超高温处理乳样中。这些蛋白几乎完全参与由二硫键连接的高分子量聚集物。通过在 pH4.6 时酸化乳来评估α-乳白蛋白和牛血清白蛋白在获得的蛋白级分中的分配情况，通过竞争性免疫测定进行。基于 ELISA 的结果表明，除了 pH4.6 不溶性β-乳球蛋白外，还可以将 pH4.6 不溶性α-乳白蛋白和牛血清白蛋白用作指示乳热处理强度的指标。
