Protease induced gelation of mixtures of alpha-lactalbumin and beta-lactoglobulin

Solutions containing 9% purified beta -lactoglobulin (beta -Lg) or alpha -l actalbumin (alpha -La) as well as mixtures of the two proteins were subject ed to proteolysis at 50 degreesC and pH 7.5 using a serine protease isolate d from Bacillus licheniformis. alpha -La was hydrolysed faster than beta -L g and the presence of beta -Lg slowed down the hydrolysis of alpha -La, whe reas hydrolysis of beta -Lg was unaffected by the presence of alpha -La. Th e solutions of the purified proteins exhibited better gelation properties t han the mixtures, presumably due to major differences in the underlying mec hanism. alpha -La produced much stronger (x 8) gels than beta -Lg under the conditions used, and in addition the gels made from alpha -La were translu cent, whereas the equivalent gels made from beta -Lg were white and opaque.