Olive leafy biomass constitutes an attractive source of biological substances, such as oleuropein, which can be valuable for the production of functional extracts. The incorporation of this valorization in a biorefinery requires understanding how feedstock and extraction conditions affect the phenolic composition. Therefore, in this study, the phenolic composition of olive leaves from nine cultivars has been explored through using conventional maceration and ultrasound-assisted extraction (UAE). Two-way ANOVA suggested that both factors have a strong influence in the total extraction yield, total phenol content (TPC), and antioxidant activity of the extracts, but only the varietal type affected the solubilization levels. Pearson correlation showed different correlation trends between the TPC and the antioxidant activity depending on the extraction method. Hence, an in-depth analysis by liquid chromatography−mass spectrometry was performed. It showed that maceration and UAE provided the same solubilization of oleuropein. Nonetheless, the cultivar and extraction method affected the qualitative and quantitative phenolic composition of the extracts, including the content of oleuropein and some novel phenolic compounds. Furthermore, using principal component analysis, the extracts were clustered in four main groups, which could be useful for further standardization in potential biorefineries placed in Tunisia.

Phenolic compounds in olive leaves have an excellent antioxidant activity and good antimicrobial properties. These bioactive molecules have beneficial properties for health, arousing great scientific and commercial interest. This study reports lyophilized olive leaf extracts (OLE) encapsulated by spray-drying using maltodextrins, maltodextrins–pectin and maltodextrins–gum Arabic as encapsulating agents. Lyophilized OLE were collected from two varieties cultivated in a harsh pedo-climatic conditions of the arid region of Tunisia. The effects of the genetic factor and the different encapsulating agents on the physicochemical properties of microcapsules and their behavior during storage, as well as their antimicrobial activities, were studied. Microcapsules successfully passed heat treatment and storage conditions and their antimicrobial activities were preserved. The encapsulating agent combination improved the encapsulation efficiency and the product yield in Zarrazi variety compared to Dhokar one. In addition, Dhokar variety microparticles showed the best heat stability at 4 and 25 °C after 90 days of storage and the higher inhibition percent against bacteria. The results of the present study evidenced that the best conditions for OLE encapsulation were obtained when the maltodextrins–pectin and maltodextrins–gum Arabic were combined to form a hybrid coating material.