Abstract: In this study, high-concentration linseed oil emulsions stabilized by egg white protein isolate were prepared by high-speed shearing. The viscoelasticity of the emulsions was determined by rheological measurements, and the distribution of the water and oil phases was investigated by measuring the conductivity. At the same time, the microstructure was evaluated by particle size distribution and laser confocal scanning microscopy analysis. Based on the above investigations, we examined the effect of oil phase concentration on properties of high-concentration emulsions. The results showed that when the egg white protein isolate concentration was maintained at 6% (m/m), the average particle size of the emulsion droplets decreased with increasing the oil phase concentration from 65% to 70% to 75% (m/m), and the degree of flocculation increased, thereby causing an overall increase in the viscosity, storage and loss modulus of the emulsion. As a consequence, the oil droplets began to be tightly compressed to exhibit a polygonal morphology. At an oil phase concentration of 80% (m/m), the average particle size of the emulsion droplets was smaller but the particle size distribution was wider; the emulsion viscosity decreased, but the storage and loss modulus increased, and the emulsion appeared gelatinous with partial aggregation of the proteins in it. The emulsion with 85% (m/m) oil phase concentration contained a large proportion of proteins that did not take part in structuring. The proteins in the emulsion were randomly aggregated and separated from the oil phase, making the emulsion unstable. This study provides a basis for understanding the formation of high-concentration emulsions, and opened up a new way to achieve value-added utilization of egg white protein.

Key words: egg white protein isolate, linseed oil, high-concentration emulsion, flocculation