Heat-induced aggregation of beta-lactoglobulin A and B with alpha-lactalbumin

beta -Lactoglobulin A and beta -lactoglobulin B were heated at 75 degreesC in the absence and presence of alpha -lactalbumin, and the aggregation prod ucts were characterized by size exclusion chromatography in combination wit h multi-angle laser light scattering and electrophoretic techniques. alpha -lactalbumin did not form aggregates when heated alone, but in admixture wi th beta -lactoglobulin it was incorporated into both the disulphide-bonded and the hydrophobically associated aggregates as well as forming alpha -lac talbumin dimers and other oligomers. The presence of alpha -lactalbumin dim inished the proportion of smaller aggregates and increased the number of ve ry large aggregates within both variant protein mixtures. In the presence o f a-lactalbumin, beta -lactoglobulin A was converted into a series of disul phide-bonded and the hydrophobically associated aggregates more slowly, but with a greater proportion of hydrophobically associated aggregates, than b eta -lactoglobulin B. These patterns: are similar to that when beta -lactog lobulin A or B are heated on their own. These and other results indicate th at the mechanism of aggregation of alpha -lactalbumin/beta -lactoglobulin m ixtures is governed by beta -lactoglobulin. (C) 2001 Elsevier Science Ltd. All rights reserved.