Physical and Oxidative Stability of Functional olive Oil-in-Water Emulsions Formulated Using Olive Mill Wastewater and Whey Proteins
Document Type Article
"Food and function" 2016,7, 227-238
The olive oil extraction process implies the production of high amounts of wastewater, rich in phenolic compounds, derivatives of oleuropein. The present paper reports on the use of these extracts added in model olive oil-in-water (O/W) emulsions to study their effects on physical and chemical stability. Spray-dried polyphenols extracted from olive mill wastewater (OMWW) were added to a model 20% olive O/W emulsion stabilized with whey protein isolate (WPI) and xanthan gum, in phosphate buffer solution at pH 7. The emulsions were characterised over accelerated storage conditions (40 °C) up to 30 days. Physical stability was evaluated by analysing the creaming rate, mean particle size distribution and mean droplet size, viscosity and rheological properties, while chemical stability was assessed through the measurement of primary and secondary oxidation products. The rheological behaviour and creaming stability of the emulsions was dramatically influenced by xanthan gum, whereas the concentration of WPI and the addition of encapsulated OMWW phenolics did not result in a significant improvement of physical stability. Interestingly, the formation of oxidation products was higher when higher concentrations of encapsulated polyphenols were used, indicating a possible binding with WPI added in the system as natural emulsifier.