Sustainable Valorization of Olive Oil By-Products: Green Extraction of Phytochemicals, Encapsulation Strategies, and Food Applications

Olive oil (OO) production generates significant amounts of by-products, including olive leaves and pruning residues, olive pomace, OO wastewater, and olive stones. These by-products are rich in bioactive compounds, particularly polyphenols and secoiridoids, which possess antioxidant, anti-inflammatory, antimicrobial, and cardioprotective properties. However, their stability and bioavailability remain challenges, necessitating innovative recovery and stabilization techniques, highlighting their potential in high-value industries such as food, cosmetics, nutraceuticals, and pharmaceuticals. This review explores the sustainable valorization of olive by-products through green extraction methods such as ultrasound-assisted extraction, microwave-assisted extraction, supercritical fluid extraction, and so on, and alternative innovative solvents like deep eutectic solvents (DES). These eco-friendly approaches enhance the recovery of bioactive compounds while minimizing the environmental impact of OO production and the reuse of its by-products. Additionally, this work explores encapsulation techniques for their effectiveness in protecting and stabilizing phenolic compounds, enhancing their solubility, bioavailability, and controlled release across various applications, including food, cosmetics, pharmaceuticals, and nutraceuticals. Recent studies highlight the effectiveness of chitosan, maltodextrin, cyclodextrin, and alginate as encapsulating agents for OO bioactive compounds, enhancing their stability. Likewise, the review emphasizes the environmental challenges arising from OO residues and discusses the potential role of olive by-products in circular economy strategies, underlining their potential in sustainable alternatives as biodegradable packaging materials to conventional paper derived from forest-based feedstocks, synthetic additives, animal feed, functional foods, dietary supplements, agricultural eco-solutions, and other applications. Moreover, it critically discusses future directions and possible challenges. The findings support the pivotal role of integrated biorefinery approaches in transforming OO by-products from agro-industrial waste into high-value resources, enhancing their efficient industrial applications, promoting sustainability and driving a force in future bioeconomies.