Olive oil micro-emulsions and study of the emulsifying ability of olive oil endogenous components

Micro-emulsions are of great importance in food industry since they are used in various food applications. In the present study edible olive oil w/o microemulsions without the addition of a co-surfactant were studied. Both chemical and natural surfactants were examined. The chemical surfactants used were Tween 20, 40, 80 and Span 20, 80. The natural substances used as surfactants were endogenous compounds of olive oil with an amphiphilic character such as gallic acid, apigenin and trans-cinnamic acid. The selection of these compounds was based on the value of their partition coefficient. The experiments proved that stable olive oil microemulsion can be prepared. According to the designed phase diagrams larger water amounts can be emulsified with the surfactants Tween 40 and Span 20. The addition of gallic acid and trans-cinnamic acid in the water phase showed significant increase of the water phase region in the phase diagrams. Moreover microemulions with olive oil endogenous compounds showed greater stability to oxidation. Statistical analysis of the data showed that the type of the surfactant affected significantly the turbidity, brightness and color of the microemulsion. Moreover the shelf life of the emulsion can be evaluated with the Stability Index. Finally it was resulted that polydispersity of the microemulsion is highly related to its viscosity and refractive index.