Interactions of proteins and surfactants at oil-water interfaces: influence of a variety of physical parameters on the behaviour of milk proteins

Displacement of adsorbed beta-casein from polystyrene latex and of caseinat e from heated and unheated soya oil and tetradecane oil-in-water emulsions by the non-ionic detergent, Tween 20, has been studied. Protein was displac ed more readily from the tetradecane emulsion than from the corresponding s oya oil. Heating decreased the amount of protein displaced from the soya oi l emulsion but had little effect on displacement from tetradecane. Ageing d ecreased the amount of protein displaced from the soya oil emulsion, but th e effects of heating were less pronounced in aged soya oil emulsions. The e ffect of pH on protein displacement from fresh and aged caseinate-stabilise d soya oil emulsions was also investigated. Protein was displaced more read ily at higher pH and, as with the beta-casein-stabilised soya oil emulsions , ageing decreased the displacement of adsorbed protein. (C) 1999 Elsevier Science Ltd. All rights reserved.