Mam. Hoffmann et Pjjm. Vanmil, HEAT-INDUCED AGGREGATION OF BETA-LACTOGLOBULIN - ROLE OF THE FREE THIOL-GROUP AND DISULFIDE BONDS, Journal of agricultural and food chemistry, 45(8), 1997, pp. 2942-2948
The heat-induced aggregation of bovine beta-lactoglobulin, dispersed i
n water at neutral pH and in different concentrations (10, 30, or 50 g
of dry matter/L), was studied at 65 degrees C, and the results are re
lated to a kinetic model. Native PAGE and SDS-PAGE analysis under nonr
educing and reducing conditions showed that on heating disulfide-linke
d aggregates were formed and that the average size of these aggregates
increased with increasing initial beta-lactoglobulin concentration. I
n the presence of the thiol-blocking agent N-ethylmaleimide (NEM), at
a molar ratio of NEM/beta-lactoglobulin monomer of 1, all thiol groups
were blocked and no disulfide-linked aggregates were formed, although
with native PAGE high molecular mass noncovalently linked aggregates
were observed. The formation of these aggregates accelerated with incr
easing NEM concentration until a molar ratio of NEM/beta-lactoglobulin
monomer of 1 was reached. In separate experiments we studied the effe
ct of pH (in the range pH 6.0-8.0) on the aggregation of beta-lactoglo
bulin and related this to the pH dependent reactivity of the thiol gro
up.