Characterization of the Maillard reaction products of beta-lactoglobulin glucosylated in mild conditions

beta -Lactoglobulin (BLG) was heated in the presence of glucose in mild con ditions leading to nonenzymatic glycation through the Maillard reaction. Th e characterization of the chromophores formed during heating at 60C showed that the modification of the UV-VIS spectrum of modified proteins was mainl y due to a condensation reaction of glucose. Amino acid analysis showed tha t at least four amino acids (lysine, arginine, histidine and tyrosine) were modified during the reaction. Modification of SDS-PAGE pattern indicated t he prevalence of a covalent polymerization of the BLG monomers independent from disulfide bridge formation. Solubility of the glucose -beta -lactoglob ulin conjugates was higher than that of heated protein at pH 5. A shift of the minimum of solubility toward acidic pH, relative to the shift of the pi of modified proteins, was observed as a function of time of glycation. Try ptic hydrolysis of the modified proteins revealed a slow glycation of Lys 6 9 as compared to Lys 70, which is consistent with its three-dimensional ori entation and its potential biological role.