Spanish olive leaf extract-loaded nanostructured lipid carriers: Production and physicochemical characterization by Zetasizer, FT-IR, DTA/TGA, FE-SEM and XRD

In this research, using ethanol/methanol/acetone-water solvents and semipreparative high-performance liquid chromatography, the phenolic compounds of the pure olive leaf were extracted. Then, the compounds were encapsulated using a proper lipid mixture and surfactant. For production of nanocarriers, a hot high-shear homogenization method accompanied with ultrasonication techniques was applied. Next, the optimum nanocarrier was investigated in terms of zeta potential, morphology, thermal behavior, chemical interactions, and crystallinity structure. Results of dynamic light scattering showed that the optimum carrier had lower values of particle size and polydispersity index than the other carriers. Structural and thermal analyses exhibited that the crystalline state of the prepared oleuropein-loaded nanocarrier was not highly ordered compared with the oleuropein-free nanocarrier. The Fourier transform infrared spectroscopy analysis showed that oleuropein was successfully accommodated inside wall materials. The sensory analysis of mayonnaise sauce samples represented no significant difference between the mayonnaise sauce containing optimum nanocarriers and the control. Practical applicationsOne of the aims of the application of nanocarriers in the food industry is to improve bioavailability, cover the undesirable odor, flavor, color, and improve solubility of some materials. Results of this work depicted that adding nanocarriers containing olive leaf extract powder as the source rich of oleuropein to the food, such as sauce, could improve the undesirable appearance, color, odor, and flavor of the extract powder (polyphenols such as oleuropein) and also enjoy high durability of antioxidant properties of the polyphenols existing in the nanocarrier. A practical opinion/idea is that encapsulation of olive leaf extract powder as nutraceutical component can be applied to nutritive and pharmaceutical industries as well as production of high-quality products with whiteness, uniformity/homogeneity, appropriate flowability, and flavor properties. In other words, the results of the present study can be used to formulate appropriate NLC to deliver oleuropein and other nutraceuticals into foods and pharmaceutical products.