Composition of fat protein layer in complex food emulsions at various weight ratios of casein-to-whey proteins

Abstract

We studied three complex food emulsions which differed only by the weight ratio of casein-to-whey proteins (80:20, 60:40, 0:100). We considered the stability of the fat droplets against aggregation/coalescence, the amount of adsorbed proteins, and the protein composition of the interface. Our results indicated that coalescence was inhibited whatever the protein composition. However, aggregation between fat droplets was observed in the casein-free emulsion (0:100), where the amount of adsorbed proteins at the fat globule surface was the lowest. Quantitative SDS-PAGE experiments showed that preferential adsorption of caseins over globular proteins occurs only in the emulsion based on the intermediate (60:40) casein-to-whey protein ratio. Furthermore, the propor- tion of adsorbed proteins which were found in polymeric forms seemed to increase with decreasing casein-to-whey protein ratio. The fat globule stability, total fat protein load and proportion of adsorbed protein in the polymeric forms were discussed in terms of adsorption properties of milk proteins at the oil-water interface, in relation to the casein-to-whey protein ratio. Milk protein / emulsion / stability / protein adsorption / disulfide bond