Foaming is one of the most important functional properties of egg white proteins. In this study, the effect of transglutaminase-induced cross-linking of egg white proteins and contamination of egg white with yolk on the foaming properties of egg white, were investigated and polysorbate 20 was used accompanied with transglutaminase in order to compensate for the deteriorative effects of the yolk on foaming ability of egg white. Enzymatic treatment increased foam stability; the longer the

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... t, the higher was the stability of foam. Optical microscopy images revealed that air bubbles coalesced much lesser in enzyme-treated egg white compared with non-treated counterpart. Nevertheless, enzymatic treatment decreased foam volume. It was argued based on apparent viscosity measurements that in enzyme-treated whites, air incorporation into the foam during white beating is decreased due to the higher consistency coefficient (K) resulting in lower foam volumes. A considerable decrease in foaming ability was observed when egg white was contaminated with yolk. Polysorbate 20 although increased the foam volume of yolk-contaminated egg white, influenced foam stability negatively. Simultaneous addition of surfactant and enzymatic treatment could compensate the weakening effect of polysorbate to some extent; however, caused a decrease in foam volume. Preferential adsorption of surfactant molecules into the air-water interface and/or evacuation of egg white proteins from the interface by surfactants might account for the observed effect of polysorbate.