Microstructure of oil-in-water low-fat emulsions containing skim milk powder and locust bean gum

Abstract

The overall purpose of this paper was to examine the microstructure of oil-in-water low fat emulsions (300 g/kg) containing skim milk powder and locust bean gum as emulsifiers/stabilizers, and to correlate the microstructural features with their rheological behaviour. Eight samples were analysed, where composition was changed within a certain range for each component. All of these showed a strong thixotropic character and yield stress. The microstructure of the samples was analysed by transmission electron microscopy. Micrographs showed casein micellar aggregates in the continuous phase of the emulsion. Also, the presence of a network structure, probably associated with protein-polysaccharide macromolecular entanglements, was evident. This macromolecular interaction also appears at the oil-water interface, where an adsorbed macromolecular multilayer surrounds the oil droplets. This feature was in agreement with a higher consistency and stability detected with increased gum and milk concentration in the emulsions. As locust bean gum is a nonionic polymer, protein-polysaccharide interactions could be favoured by the low pH of the samples within the isoelectric range of caseins, and by the high level of the ionic strength, which could exert an additional neutralizing effect on the ionic groups of proteins. ©1996 Academic Press Limited.