Oxidative stability of oil-in-water emulsions stabilised with protein or surfactant emulsifiers in various oxidation conditions

Many studies have investigated the effect of emulsifiers on the oxidative stability of oil-in-water (O/W) emulsions. A better oxidative stability of surfactant-stabilised O/W emulsions as compared to protein-stabilised emulsions has been recently shown in conditions when the major part of the emulsifier is adsorbed at the oil–water interface and oxidation is induced by iron−ethylenediaminetetraacetic acid (EDTA) complex. In this work, the contribution of the interfacial layer to the oxidation of emulsified lipids is investigated under various incubation conditions, involving different oxidation mechanisms. O/W emulsions were formulated at pH 6.7 with limited amounts of emulsifiers in the aqueous phase. Emulsions were incubated either at 33 °C without initiator at 25 °C in the presence of iron/ascorbate, metmyoglobin or 2,2′-azobis(2-amidinopropane)-dihydrochloride (AAPH). Oxygen uptake and volatile compound formation confirmed that protein-stabilised emulsions are less oxidatively stable than Tween 20-stabilised ones. This work also shows complex oxidative interrelationships between oxidation initiator and certain proteins, such as β-casein and bovine serum albumin.