The role of endogenous amphiphiles on the stability of virgin olive oil‐in‐water emulsions

Stable virgin olive oil‐in‐water emulsions were prepared using total endogenous surface‐active components derived from oil as emulsifying agents, and the interfacial properties of the emulsion droplets were examined. The amount of oil extracted into the aqueous buffer increased with buffer pH, with the most stable emulsions being formed at pH 7.5. Light microscopy of the emulsions revealed the presence of spherical droplets with diameters ranging from 1.5 to 3 μm. Their surface was negatively charged at pH 7.5, as confirmed by the effect of ions and polycations. Potassium chloride, Ca 2+ , and spermine induced rapid aggregation (as monitored by the turbidity change and by light microscopy), showing their maximal effect at 1 M, 4 mM, and 60 μM, respectively. Papain treatment of the emulsion particles rapidly induced particle aggregation, suggesting the destruction of stabilizing structural olive oil proteins. Unlike papain, treatment with phospholipase C did not result in an appreciable turbidity change. Treatment with soybean lipoxygenase slightly increased the turbidity of the emulsion. The interaction of linoleate‐Tween 20 mixed micelles with emulsion droplets produced turbidity, which was maximal at a neutral pH, whereas interaction with proteolyzed and lipoxygenase‐treated droplets induced both a significant increase in turbidity and a red shift to a different absorption maximum of the system as compared with those of the untreated emulsion.