Effect of pH on the interfacial and foaming properties of Maillard reaction-modified proteins

The interfacial and foaming properties of two conjugates obtained by Maillard reaction was determinate, at heating times of 36 and 60 h. The effect of covalent interaction between β-lactoglobulin (β-Lg) and two dextran molecular weights (10 and 20 kDa) were evaluated at pH 7 and pH 5, establishing protein controls, mixed systems, and mixing controls for each system. At pH 7, the first conjugate showed an increase in surface activity, while the other showed an opposite effect on the glycosylation process. At pH 5, both conjugates showed a low surface activity, evidenced in the diffusion constants. Less foaming stability was observed at pH 5, compared to pH 7, related to the formation of protein aggregates due to the proximity to their pI. Both conjugates showed greater stability, at both pH 7 and pH 5, with respect to their control systems, due to greater steric-type interaction forces between adjacent bubbles when the interface could be stabilized by glycosylates than when there is only protein. These results indicate that glycosylated b-Lg could find use as an additive and foaming agent, particularly in acidic foods.