Physicochemical studies on wheat protein foams. II. Relationship between bubble size and stability of foams prepared with gluten and gluten components

Abstract

An investigation was made to obtain information on the foam properties of gluten and its component proteins (gliadin and glutenin) through measurements of bubble size, rate of coalescence, and lifetime of a series of single bubbles at an air/water interface. Near the isoelectric point of the proteins, the rate of coalescence between the bubbles in foam attained a minimum, while the lifetime of the bubbles attained maximum. Glutenin foam was prominently more stable than the other protein foams at any given pH values. These results are consistent with the foam stability obtained from the rate of foam drainage. On the other hand, the bubble size of the protein foams increased progressively up to the isoelectric point of the proteins. The bubble size of glutenin foam was significantly larger than that of the other protein foams at any given pH values. By cleaving and blocking disulfide bonds the bubble size and coalescence rate of glutenin foam significantly decreased, while lesser changes were observed with gluten or gliadin foam.