Stabilisation of protein adsorbed layers in foams and emulsions by crosslinking

Foams and emulsions which are stabilised by proteins e.g. beer foams and meringues remain stable in the absence of small molecular weight surface active components (lipids, emulsifiers and surfactants). In the presence of surfactants the stabilising visco-elastic layer of protein surrounding each particle is compromised due to competitive adsorption of the surfactant. One strategy to overcome these partially stable dispersions is to unite the 'mobilised' regions of protein adsorbed at the airwater or oil-water interface and produce a more continuous layer of adsorbed protein. A model foam composed of precise amounts of surface active protein, ßlactoglobulin (ß-lg) and an emulsifier, Tween 20, to mimic the destabilistion of food foams and emulsions was used as a test sample to assess the effectiveness of various potential crosslinking agents. Additk)n of micromolar concentrations of the polyphenol, (+)catechin and a trivalent cation, AI3+ were found to increase the foam formation and foam stability (reduced liquid drainage from the foam). Behaviour of the model foams has been related to the (+)catechin and trivalent cation mediated crosslinking of protein adsorbed at the interface in thin liquid films (foam lamellae)