Enzymatic cross-linking at oil-water interfaces – a rheological study

Potential food-compatible technologies for novel oil-in-water emulsions include interfacial cross-linking by enzymatic means. The objective of the present research is to elucidate the mechanisms, by which protein interfaces control transfer of low molecular weight compounds. As a first step, the impact of enzymatic cross-linking on mechanical properties of -casein layer was studied. The dependence of interfacial properties on bulk phase concentration suggests, that the dynamics of cross-linking are influenced by the thickness and/or packing of the interfacial layer. INTRODUCTION Many food products are complex emulsions and their stability is greatly dependent on mass transfer phenomena. Oxidative stability and taste-masking are often major concerns especially in foods including unsaturated fatty acids or other health promoting components. The primary stage of oil oxidation involves transfer of oxygen across the interface from the aqueous phase to the dispersed oil phase. Mass transfer related instability is also caused by volatile secondary oxidation products, which can penetrate the interfacial layer and subsequently deteriorate the sensory quality of the product due to their low odour thresholds. Therefore, the properties of the interfacial layer are the key in controlling oxidative stability of oil-in-water emulsions. Proteins play a central role in formation and stabilisation of food emulsions. Food proteins although very different in size and structure and hence, in adsorption dynamics, are still quite similar in terms of their interfacial rheology and charge. Technologies for engineering their interfacial behaviour are needed. Potential food-compatible technology for these novel oil-in-water emulsions is an interfacial cross-linking by enzymatic means. The objective of the present research is to elucidate the mechanisms, by which protein interfaces control transfer of low molecular weight compounds. As a first step, the impact of enzymatic cross-linking on the mechanical properties of the interfacial layer