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.

Research background. Food by-products such as onion peels and olive leaves are rich in bioactive compounds applicable as natural and low-cost sources of antioxidants. Still, these compounds mainly exist in glycosylated form. Often, hydrolysis of glycoside compounds increases their antioxidant activity and health benefits. However, not many studies have been done concerning the β-glucosidases effect, specifically from A. niger, on glycosylated compounds within these by-products. Also, changes in the antioxidant activity of the mentioned by-products under the effect of β-glucosidase have not been reported yet. Therefore, this study considered the effect of Aspergillus niger β-glucosidase on glucoside compounds and the antioxidant activity of onion peel and olive leaves extracts. Experimental approach. The antioxidant activity of the extracts was assayed by DPPH and FRAP tests. Also, glucose, total phenolic, and flavonoid content were measured. Moreover, TLC and HPLC analyses were applied before and after the enzymatic hydrolysis. Results and conclusions. The obtained results showed an increase in the extract antioxidant activity after treatment. Also, an enhancement was observed in the extracts glucose content by β-glucosidase. The TLC and HPLC results showed the β-glucosidase efficacy to hydrolyze quercetin glucosides in onion peel extract, and the quercetin content was increased from (0.479±0.04) mg/mL in the untreated extract to (1.262±0.027) mg/mL in the treated extract (0.5 % m/V) after 3 h enzymatic hydrolysis at 45 °C. Also, the content of quercetin-3-O-glucoside was increased considerably from (0.0018±0.0001) to (0.054±0.009) mg/mL following enzyme treatment. Moreover, oleuropein in olive leaves extract (1 % m/V) was hydrolyzed completely from (0.382±0.016) to 0 mg/mL by β-glucosidase for 24 h at 50 °C. Novelty and scientific contribution. This study showed that A. niger β-glucosidase, as a stable enzyme, hydrolyzed quercetin and oleuropein glycosides in onion peel and olive leaves extracts. Thus, A. niger β-glucosidase is a good candidate for processing the food waste and extracting valuable bioactive compounds. Also, the treated extracts with higher antioxidant and biological activity, and without bitterness can be applicable as potent, natural, and cost-effective antioxidants in the food industry.

ABSTRACT. The milk along with xanthan at levels 0, 1.9, 3.9, 5.9, 7.9, 9.9 and 0.1 and 0.2 % (No 1 (control) to 11 respectively) as egg replacement were used for preparation of mayonnaise. Creaming index, heat stability, physical stability and rheological properties of samples over a were investigated. Also flow behavior of samples were fitted to Power law, Herschel-Bulkley and Casson models. It was found that addition milk along with xanthan to mayonnaise protected from phase separation in comparison to control sample. All the samples had stability higher than 99% except samples 1, 4, 5 and 6. The highest stability was recorded for sample No 11 (99.98%) and the lowest for 5 (74.95%) that compared with control sample had significant differences (p> 0.05). All the samples except No 1 and 5 showed heat stability higher than 99 % and the highest stability recorded for No 11 ( 99.72%) and the lowest for No 5 (67.42 %) and in comparison with control were significantly different (p> 0.05). Apparent viscosity decreased with increase the egg replacement from 40% to 80%, as the highest and lowest viscosity observed in samples contain 100% and 80% replacement respectively. All samples showed shear-thinning behavior and the high coefficients of determination for Power law and Herschel-Bulkley models (0.99) revealed the adequacy of these rheological models to describe flow behavior of mayonnaise.

The milk along with xanthan at levels 0, 1.9, 3.9, 5.9, 7.9, 9.9 and 0.1 and 0.2 % (No 1 (control) to 11 respectively) as egg replacement were used for preparation of mayonnaise. Creaming index, heat stability, physical stability and rheological properties of samples over a were investigated. Also flow behavior of samples were fitted to Power law, Herschel-Bulkley and Casson models. It was found that addition milk along with xanthan to mayonnaise protected from phase separation in comparison to control sample. All the samples had stability higher than 99% except samples 1, 4, 5 and 6. The highest stability was recorded for sample No 11 (99.98%) and the lowest for 5 (74.95%) that compared with control sample had significant differences (p> 0.05). All the samples except No 1 and 5 showed heat stability higher than 99 % and the highest stability recorded for No 11 ( 99.72%) and the lowest for No 5 (67.42 %) and in comparison with control were significantly different (p> 0.05). Apparent viscosity decreased with increase the egg replacement from 40% to 80%, as the highest and lowest viscosity observed in samples contain 100% and 80% replacement respectively. All samples showed shear-thinning behavior and the high coefficients of determination for Power law and Herschel-Bulkley models (0.99) revealed the adequacy of these rheological models to describe flow behavior of mayonnaise.

Because of health concerns regarding synthetic antioxidants, natural antioxidant compounds are being considered by scientists. Bioactive peptides have been shown to have various physiological functions, such as antioxidative activity. Pomegranate seed protein, the by-product of the pomegranate seed oil industry, can be a good source of bioactive peptides. The optimum conditions for enzymatic hydrolysis of pomegranate seed protein with alcalase were determined using a response surface methodology. The influence of different temperatures (45-55 °C), times (30-180 min), and enzyme to substrate (E/S) ratio (1-3% w/w) on DPPH scavenging power and ferric reducing activity as the responses, were studied. Also, the degree of hydrolysis and the surface hydrophobicity of samples were determined. Moreover, using scanning electron microscopy and electrophoresis technique, microscopic structure and molecular weight of hydrolysate, were studied respectively. Alcalase-derived hydrolysates showed a DPPH scavenging activity (88 ± 0.97 %) and ferric reducing power (0.5 ± 0.83) at optimum conditions of hydrolysis (48.8°C, 97.5 min, E/S ratio 1.3%w/w). The degree of hydrolysis coincided with 36 ±1.2%. An increase in the surface hydrophobicity of the protein during hydrolysis confirmed the unfolding of the pomegranate seed protein structure. The presence of low-molecular-weight peptides was evidenced by the electrophoresis technique. As well as the SEM showed that protein fragments had been reduced to small sizes following enzymatic treatments. According to the results of this study, pomegranate seed protein hydrolysate can be considered a suitable source of antioxidants with an aggregate market value in food formulations