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 β-casein from polystyrene latex and of caseinate from heated and unheated soya oil and tetradecane oil-in-water emulsions by the non-ionic detergent, Tween 20, has been studied. Protein was displaced more readily from the tetradecane emulsion than from the corresponding soya oil. Heating decreased the amount of protein displaced from the soya oil emulsion but had little effect on displacement from tetradecane. Ageing decreased the amount of protein displaced from the soya oil emulsion, but the effects of heating were less pronounced in aged soya oil emulsions. The effect of pH on protein displacement from fresh and aged caseinate-stabilised soya oil emulsions was also investigated. Protein was displaced more readily at higher pH and, as with the β-casein-stabilised soya oil emulsions, ageing decreased the displacement of adsorbed protein.