The present study sought to encapsulate oleuropein as a nutraceutical compound in order to investigate its physical properties and stability. We extracted the phenolic compounds of virgin olive leaf by ethanol-water and acetone-water solvents. The purity of this extract was confirmed by analytical high-performance liquid chromatography using oleuropein standard. Oleuropein was encapsulated with different components (lecithin, linoleic acid, glycerol monostearate, soybean oil, and Tween 80), and the effect of their contents on oleuropein-nanostructured lipid carrier (NLC) characteristics was checked by dynamic light scattering test. Moreover, several features of the optimal nanocarrier, including zeta potential, structural, morphology, stability, as well as thermal behavior were studied. The results of optimal NLC exhibited a high zeta potential as well as supreme stability versus aggregation. Thermal study indicated that oleuropein was well embedded into NLCs. The scanning electron microscope images showed that NLC samples had many spherical particles in the form of chain structure. The stable nanocarriers did not exhibit any oleuropein leakage following their analyses for 90 days at -18, 6, and 25 °C in aqueous suspension.

Kefiran is an exogenous microbial metabolite which is produced principally by lactic acid bacteria and fungi and molds throughout growth. Exo polysaccharide of kefiran was extracted from kefir grains and in status of gel was added at 1, 2, 3% concentrations (w/w flour basis) to wheat flour to evaluate its effects on rheological properties of weak wheat dough. The rheological measurements of the dough were investigated using Farinograph and Extensograph instruments. Results of Farinograph evaluation of dough showed that adding of kefiran and increase in its levels leads to increase in the water absorption capacity, dough development time and departure time, while the dough degree of softening after 20 min and mixing tolerance index were decreased in comparison with the control sample. The study on Extensograph behavior of the dough containing kefiran showed that resistance to extension at 45 and 90 min resting times was increased by increasing the percentage of the added kefiran. Longer fermentation time for each level of kefiran led to decrease of resistance to extension. Significant difference was observed in the resistance to extension of the dough containing different levels of kefiran and the control sample. Addition of kefiran to the dough after 45, 90 and 135 min resting times significantly decreased the extensibility, also with an increase in resting time from 45 to 135 min, the extensibility decreased for both the control and kefiran samples. Generally, addition kefiran at 45, 90 and 135 min resting times led to a significantly increase in resistance to extension ratio. Energy input increased at 45 and 90 min resting times, whereas chaotic effect was shown at time of 135 min restig time. Therefore, kefiran can be used to playing an important role in improving of rheological properties of weak dough and its processing conditions.

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 applications One 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.

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