Recovery of bioactive compounds from citrus by-products: advances in conventional and innovative extraction approaches, bioavailability, and applications

Citrus processing generates large amounts of by-products-mainly peels, pomace, and seeds-that are abundant in valuable bioactive compounds such as polyphenols, carotenoids, essential oils, pectin, and vitamin C. Efficient recovery of these compounds not only supports the production of functional ingredients but also aligns with circular economy and zero-waste objectives. Traditional extraction methods, including maceration, Soxhlet extraction, hydrodistillation, and solvent extraction, remain widely used but often require long processing times, consume significant energy and solvents, and can degrade heat-sensitive molecules. In recent years, greener and more innovative technologies-such as ultrasound-assisted, microwave-assisted, enzyme-assisted, supercritical fluid, pressurized liquid, pulsed electric fields, and deep eutectic solvent extractions-have emerged as sustainable alternatives, achieving higher yields and better compound stability with lower environmental impact. This review provides a critical comparison of conventional and emerging extraction methods, evaluating their efficiency, selectivity, scalability, and environmental performance. It also explores how these techniques influence the bioavailability and bioaccessibility of extracted compounds. Furthermore, potential applications of citrus by-product extracts in the food, nutraceutical, cosmetic, and agricultural sectors are discussed. Finally, the review addresses key technological, economic, and regulatory challenges related to industrial implementation and highlights future opportunities for integrating these extraction strategies into circular bioeconomy models.