Valorization of selected fruit and vegetable wastes as bioactive compounds: Opportunities and challenges

Fruit and vegetable wastes derived from the agri-food industry are generated in large amounts and they can cause great environmental contamination because they have a high moisture content and microbial load. However, both their structural parts (stems, leaves, peels, pulps, seeds, and roots) and the residues resulting after the extraction of their juices are rich in different valuable compounds such as antioxidants, oils, fiber, fatty acids, isoprenoids, lipids, proteins, saponins, and phytoestrogens. Such bioactive compounds can be used as pharmaceutical excipients, food additives, or included in pharmaceutical formulations or food matrices for obtaining nutraceutical products and functional foods, respectively. The aim of this review is to present the most promising alternatives for the valorization of selected fruit and vegetable wastes, currently underexploited, as well as the challenges that may arise when considering the valorization of these wastes in the form of value-added bioactive products. This is exemplified through the revision of the opportunities offered by artichoke, cardoon, asparagus, and pomegranate, which generate large amounts of waste during their processing. A final section is devoted to present the emerging technologies that are being developed for an efficient extraction of bioactive compounds from vegetable matrices.