Characteristics of oil–water emulsions stabilised by an industrial α-lactalbumin concentrate, cross-linked before and after emulsification, by a microbial transglutaminase

Industrial α-lactalbumin concentrate, cross-linked with a microbial transglutaminase, showed lower dilational surface viscosity at a planer oil–water interface than a non-cross-linked α-lactalbumin concentrate. Properties of emulsions containing cross-linked α-lactalbumin were influenced by the sequence of cross-linking and emulsification. Emulsions stabilised by α-lactalbumin concentrate (even without crosslinking) were generally unstable. While cross-linking before emulsification decreased the stability further, the emulsion stability was improved when cross-linking was carried out after emulsification. Results from the sodium dodecyl sulphate (SDS) gel electrophoresis of adsorbed protein suggested that, irrespective of the sequence of cross-linking and emulsification, the adsorbed protein was polymerised too extensively to be resolvable on the gel matrix. Results from the reverse-phase HPLC suggested that the amount of adsorbed protein in emulsions containing protein cross-linking before emulsification was lower than that containing cross-linking after emulsification.