Glycosylation of individual whey proteins by Maillard reaction using dextran of different molecular mass

Glycosylation of the whey proteins β-lactoglobulin (β-Lg), α-lactalbumin (α-La) and bovine serum albumin (BSA) with dextran of 10 and 20 kDa was undertaken by the Maillard reaction. The effect of the molecular mass of the polysaccharide on the molecular characteristics and the solubility and thermal stability of the conjugates was investigated. The experimental conditions (60 °C, 0.44aw, weight ratio protein:polysaccharide 1:2) were selected to give the highest level of furosine formation in order to restrict advanced stages of the reaction. The degree of glycosylation of the conjugates purified by ultrafiltration, as calculated from the blocked Lys extracted from the furosine level was in the order: BSA>β-Lg>α-La. However, comparatively, the amount of unreacted β-Lg exceeded that of the other two proteins. Regardless of the type of protein, higher levels of glycosylation were found when dextran of 10 kDa was used as compared to dextran of 20 kDa. The attachment of the polysaccharides improved the solubility of the three proteins at acidic pH and enhanced the heat stability of β-Lg and BSA, the most thermally unstable proteins. The relationship between the molecular weight of the polysaccharide, the structural modifications and the functionality of glycosylated proteins is discussed.