Effect of the dry-heating conditions on the glycosylation of β-lactoglobulin with dextran through the Maillard reaction

The effect of the reactants weight ratio, temperature, water activity (aw) and heating time on the degree of conjugation of β-Lg with a high-molecular weight dextran was investigated. A central composite face design was used to carry out an optimisation of the reaction conditions leading to the maximum formation of the Amadori compound, with the concentration of furosine as response variable. According to the model, the optimum conditions to achieve maximum formation of the Amadori compound were 60 °C, 0.44 aw and 2:1 weight ratio of dextran to β-Lg. In addition, a different combination of conditions (55 °C, 0.65 aw and 6:1 weight ratio of dextran to β-Lg) was selected to investigate its effects on the characteristics of the conjugates formed during 14 days of dry-heating. The former conditions led to a quick conjugation that then slowed down due to further modification of the amino groups to give protein aggregation. The combination of lower temperature and higher aw, and dextran concentration promoted brown colour development and polymerization of the protein, probably through an increase in the number or reactive intermediates.