Date

2023-1-27

Author

Sönmezler, Demet

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Olive leaves are obtained as a waste product in olive and olive oil production. Biophenols, abundantly found in olive leaves, has well-known health benefits and can be used in dietary supplements, nutraceuticals, or functional food ingredients. However, the sensitivity of biophenols to heat, light and oxidizing agents necessitates the development of various methods, such as encapsulation, to increase their bioavailability. Undesired sensorial properties of the extract can also be masked by encapsulation. In this study, double emulsions were preferred as an encapsulation method owing to the protective effect it provides to the active substance and the control over its release. W/O/W type of double emulsions was prepared considering the water solubility of olive leaf extract. The effect of different pea flour concentrations (15%, 20%, 25%) and different homogenization methods (high-speed homogenization, ultrasonication) on emulsion properties was experimented. The prepared emulsions were characterized with respect to their particle size, rheology, encapsulation efficiency, stability, optical images and release behavior. As hypothesized, flours acted as emulsifiers in the outer aqueous phase to increase the stability of emulsions. It was observed that both the long-term and instant stability of emulsions were correlated with the viscosity and particle size. Increasing pea flour concentration from 15% to 25% resulted in a 25% increase in the stability of double emulsions prepared with high-speed homogenization (HSH) and a 30% increase in emulsions prepared with ultrasonication (US). The higher stability of emulsions prepared with 25% was due to their higher viscosity and smaller particle size. Storage temperature also affected the stability of emulsions as emulsions stored at 20°C showed faster degradation compared to 4°C. Moreover, due to the lower viscosity, this effect was more prominent in emulsions in which 15% pea flour was employed. US treatment did not decrease the average particle size of emulsions. Average encapsulation efficiency values for double emulsions prepared with HSH and US were 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 double emulsion method.

Subject Keywords

Olive leaf extract, Double emulsion, Encapsulation, Pera flour, Ultrasonication

URI

https://hdl.handle.net/11511/102000

Collections

Graduate School of Natural and Applied Sciences, Thesis