MOLECULAR-MASS DISTRIBUTIONS OF HEAT-INDUCED BETA-LACTOGLOBULIN AGGREGATES

The aggregates in heated bovine beta-lactoglobulin solutions were sepa rated by high-performance size-exclusion chromatography, and molecular characteristics were measured on-line using multiangle laser-light sc attering detection (SEC-MALLS). This technique was proven to be a very useful and valuable approach for characterization of heat-induced bet a-lactoglobulin aggregates. Using TSK G2000 SWXL and TSK G4000 SWXL si lica gel columns connected in series, aggregates up to a molecular mas s of 4 x 10(6) Da could be separated, and complete molecular mass dist ributions were derived. Up to a molecular mass of 1.5 x 10(6) Da the m olecular masses calculated by the MALLS agreed very well with the resu lts obtained by conventional calibration. The measured molecular mass distributions of the heat-induced beta-lactoglobulin aggregates varied strongly with experimental heating conditions (beta-lactoglobulin con centration, pH, heating temperature, ionic strength). The results obta ined with several beta-lactoglobulin concentrations at neutral pH were consistent with a kinetic aggregation model based on thiol/disulfide exchange reactions. The average molecular mass and the radius of gyrat ion of the heat-induced beta-lactoglobulin aggregates increased with i ncreasing initial beta-lactoglobulin concentration.