EFFECT OF ASCORBIC-ACID ON THE FOAMING AND GELLING OF GLOBULAR-PROTEINS

Foam expansion and foam stability of plasma and egg albumen proteins were enhanced in the presence of increasing concentrations of ascorbic acid (0.1-1.0%). BSA showed the greatest improvement in foaming properties following treatment with ascorbic acid, whilst foaming properties of egg albumen were improved to a limited extent. A combination of partial acid hydrolysis and treatment with 1% ascorbic acid was required to dramatically improve the foaming properties of bovine blood plasma. In the presence of sucrose, foam expansion of both native and ascorbic acid-treated blood plasma was decreased. In contrast the foam expansion of ascorbic acid-treated egg albumen was greater although this effect decreased slightly on incubation. The gelation of ascorbic acid treated proteins increased with increasing temperatures over 80-90 degrees C, particularly for BSA and blood plasma, and with increasing concentrations of ascorbic acid. Ascorbic acid-treated proteins exhibited enhanced surface and exposed hydrophobicity and reduced numbers of sulphydryl groups indicating the involvement of these factors in foam and gel formation.