Effect of transglutaminase-induced cross-linking of sodium caseinate on the properties of equilibrated interfaces and foams

The effect of transglutaminase (TG)-induced cross-linking on interfacial rheology and foam stability was investigated in sodium caseinate systems. Higher dilatational surface moduli values were found, when cross-linking was performed at an equilibrated interface. However, cross-linking prior to adsorption was not found to affect the moduli values. but increased the equilibrium surface tension value. Foaming ability of cross-linked sodium caseinate was little reduced, when short reaction times with the enzyme were used, but a considerable loss in foaming ability was observed with extensive cross-linking prior to foaming. Stability against drainage was increased with increasing reaction time. With 15 min reaction at 40 C with 200 nkat/g TG, no liquid drainage was observed 2 It after foaming from 10% sodium caseinate foam. Much smaller bubbles were found in enzyme-treated foams as compared with the reference sodium caseinate foam at 30 min, 2 It and 24 h after foaming. TG-treatment retarded but did not inhibit bubble coarsening in foams. Most likely, the effects in stability were due to increase in continuous phase viscosity. (C) 2009 Elsevier B.V. All rights reserved.