Study of olive oil-in-water emulsions with protein emulsifiers

The rheological properties and oxidative stability of oil-in-water emulsions (O/W) with olive oil stabilized by soy protein isolate (SI) and whey protein isolate (WPI) were investigated. The emulsions were prepared at oil phase volume concentrations ranging from 30 to 70% v/v and emulsifier concentrations ranging from 4 to 8 wt%. The emulsions exhibited Newtonian or pseudoplastic behaviour at lower oil and emulsifier concentrations and plastic behaviour at higher concentrations. In addition, the emulsion stability against creaming over storage period was determined. It was established that the emulsions at lower oil concentration were less stable. The creaming stability correlated well with the viscosity of dispersive systems. The differences in the oxidation processes were evaluated by measuring the formation of primary and secondary oxidation products. It was shown that the emulsions with lower olive oil volume concentration were less stable than the emulsions with higher one. The bulk olive oil was more stable than the O/W emulsions both with SI and WPI.