The effect of freeze-drying and gamma irradiation at 0.5, 1, and 2 kGy on the physicochemical composition (moisture, fat, ash, mineral, and chlorophyll contents), microstructure, total phenolic content, and antioxidant capacity of stevia leaves was investigated in the present study. The results obtained indicated that freeze-drying and gamma irradiation treatments caused significant reduction ( p  ≤ 0.05) of moisture and fat contents in comparison with those of commercial leaves, while ash content was not significantly affected. Mineral composition was analysed. Among the analysed elements, potassium and iron levels were higher in the freeze-dried and irradiated samples, respectively. The microstructure was analysed using a scanning electron microscope. Micrographs revealed that a higher porous size structure was obtained by freeze-drying, and degradation of cell wall structure was more clearly visualized by irradiation at 2 kGy. However, the main functional groups were stable as confirmed by Fourier transform infrared spectroscopy analysis. The effects on chlorophyll content, phenolic profile, and antioxidant properties were evaluated before and after ten months of storage. In terms of chlorophyll contents, the freeze-dried leaves exhibited the highest content. Chlorophylls a and b decreased when storage progressed for freeze-dried leaves as well as for gamma-irradiated leaves. Both preservation methods gave significant advantages in increasing the total phenolic content and DPPH scavenging activity. Moreover, a significant increase of bioactive compounds and antioxidant activity was observed as the gamma irradiation dose increased. In addition, the storage time increased the amounts of polyphenols and DPPH scavenging activity. After 10 months of storage, gamma-irradiated leaves had the highest total phenolic content as well as the DPPH scavenging activity followed by freeze-dried leaves. The results indicate that freeze-drying and gamma irradiation at the studied doses could be effective postharvest methods for preservation of stevia leaf quality.

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The Moroccan picholine tree’s leaves contain phenolic compounds that benefit human health. However, the amount and type of these compounds can vary based on factors such as the extraction method and conditions. This study aimed to improve phenolic compounds’ extraction while minimising harmful chemicals’ use. It has been found that using ethanol as a solvent with ultrasonic extraction is the most effective and environmentally friendly technique. Several parameters, such as the extraction time, solid/solvent ratio, and ethanol concentration as independent variables, were evaluated using a surface response method (RSM) based on the Box–Behnken design (BBD) to optimize the extraction conditions. The experimental data were fitted to a second-order polynomial equation using multiple regression analysis and also examined using the appropriate statistical methods. In optimal conditions, the ultrasonic time, the ratio (solvent/solid) and the concentration (ethanol/water), the content of total polyphenols (TPC), total flavonoids (TFC), and antioxidant activity (by DPPH, ABTS, FRAP) were, respectively, 74.45 ± 1.22 mg EAG/g DM, 17.08 ± 1.85 mg EC/g DM, 83.45 ± 0.89% 82.85 ± 1.52%, and 85.01 ± 2.35%. The identification of phenolic compounds by chromatography coupled with mass spectrum (HPLC-MS) under optimal conditions with two successive extractions showed the presence of hydroxytyrosol, catechin, caffeic acid, vanillin, naringin, oleuropein, quercetin, and kaempferol at high concentrations.

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Argania spinosa L. Skeels is an emblematic tree in Morocco, known worldwide for its medicinal and nutritional value. Its fruits contain kernels used to prepare an edible oil, the leaves are used to feed livestock, and its wood is used as fuel. If the oil acquires high importance, the other components of the fruit of the argan are undervalued. Our objective is to invest the waste of the argan industry. Particularly, our study aimed to assess the effect of thermal activation of argan pulp on its therapeutic value, its phenolic profile and its functional and physicochemical properties. After heat treatment, the HPLC analysis for the average total phenolic content varied from 2% to 37%, depending on temperature. The antioxidant activity was increased with heat treatment. Higher values of antioxidant activity, polyphenol and pigment content were recorded at 70 °C. Functional properties analysis indicated that water solubility index and water absorption capacity were significantly affected by heat stress. Physicochemical analysis showed that moisture content, titratable acidity and soluble solids were affected.