Encapsulation of olive leaf extract using double emulsion method

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Olive leaves are obtained as a waste product of the olive industry. Biophenols, abundantly found in olive leaves, are susceptible to heat, light, and oxidizing agents, which necessitates encapsulation to increase their bioavailability. In this study, the double emulsion method was preferred due to its protective effect on the active substance and the control over its release. The effects of different pea flour concentrations (15%, 20%, and 25%) used in outer aqueous phase of double emulsion and homogenization methods [high-speed homogenization (HSH) and ultrasonication (US)] on emulsion properties were investigated. The particle size, rheology, encapsulation efficiency, stability, optical images, and release behavior of the emulsions were determined. As hypothesized, flours acted as emulsifiers in the outer aqueous phase to increase the stability of emulsions. It was observed that the stability of emulsions was correlated with the viscosity and particle size. Increasing pea flour concentration from 15% to 25% resulted in a 25% and 30% increase in the stability of double emulsions prepared with HSH and US, respectively. The higher stability of emulsions prepared with 25% was due to their higher viscosity and smaller particle size. Samples were found to have shear-thinning behavior. Moreover, emulsions stored at 20 °C showed faster degradation compared to 4 °C. US treatment did not decrease the average particle size of emulsions. Average encapsulation efficiency for double emulsions prepared with HSH and US was 88.3% and 85.9%, respectively. As a result, pea flours could be used to encapsulate olive leaf extract successfully with high encapsulation efficiencies by using the double emulsion method.