Valorisation of Citrus Processing Waste with Special Emphasis on Lemon: Bioactive Compounds, Extraction Techniques, and Sustainable Applications

Abstract

A substantial proportion, which is approximately 40-50% of the biomass, is discarded as waste in the form of pomace, seeds and peels from the citrus fruits such as lemon. The generation of large quantities of agro-industrial wastes has increased the rapid expansion of the worldwide fruit processing industry. The residues, which are traditionally considered waste, pose a significant environmental challenge. With diverse therapeutic & functional properties, the recent studies highlight that those citrus wastes are a rich source of valuable biologically active compounds, including flavonoids, pectin, phenolics, essential oils & dietary fibres. By exploring the extraction methods, industrial applications & composition, this review focuses on the valorisation of citrus wastes with a special emphasis on the lemon-based by-products. In terms of sustainability & efficiency, both conventional extraction techniques and modern advanced green technologies are used, such as supercritical fluid, microwave-assisted, ultrasound-assisted & enzyme-assisted extractions. Moreover, Pectin has gained a huge significant attention due to its wide applications in pharmaceutical, food & biodegradable packaging industries among all other recovered compounds. In addition, citrus wastes can also be changed or transformed into value-added products such as functional foods, biofuels, biopolymers, eco-friendly packaging materials and nutraceuticals, supporting sustainable development and circular bioeconomy. Challenges related to large-scale implementation, process optimisation, and cost remain a major concern despite all these advancements. For the conversion of citrus waste into valuable bioresources while reducing the environmental impact and promoting a sustainable industrial practice, waste valorisation offers a promising and strong strategy.