Foaming and interfacial properties of wheat gluten hydrolyzates

Controlled enzymatic hydrolysis of gluten, a co-product of the industrial wheat starch isolation process, increases its solubility in aqueous media and can produce hydrolyzates with foam formation and stabilization properties. Commercial wheat gluten was hydrolyzed to different degrees of hydrolysis (DH, determined with pH-stat) using trypsin (DH1, DH2 and DH6) and pepsin (DH2, DH6 and DH10). The foaming properties of the resulting hydrolyzates were evaluated by a standardized whipping procedure and related to apparent molecular weight distribution, hydrophobicity and amino acid composition. In addition surface active properties of the hydrolyzates were evaluated by studying adsorption kinetics (dynamic surface tension) and protein film elasticity. These results can be related to foaming properties (foam formation and foam stability). Hydrolyzates with low DH contained more smaller peptides and resulted in higher foam stability than those with high DH. Tryptic hydrolyzates were more hydrophilic than peptic hydrolyzates. No large difference in foaming properties could be distinguished between these two but small peptic hydrolyzates seemed to show a slightly faster adsorption speed than tryptic hydrolyzates. Foam stability was related to elasticity of the protein film. Finally, the influence of sucrose on the foaming and interfacial properties of the different hydrolyzates was investigated.status: publishe