Peels, seeds, shells, cores and pomace are major by-products of fruit processing, whose improper disposal poses critical environmental and economic challenges. Currently, there is a growing need to find strategies for recycling and valorising these by-products, now recognised as valuable sources of bioactive compounds for nutraceutical, cosmetic and agrochemical applications. This review explores the by-products of the most important Mediterranean fruits and nuts, examining their bioactive composition and potential applications to identify understudied matrices and compounds, thus determining research gaps and priorities for their valorisation. Among waste matrices, pome cores, stone fruit pomace, seeds and internal layers of citrus, pomegranate pulp, and nut shells and skins were the most overlooked. Furthermore, some classes of phytochemicals, including phytosterols of stone fruits and triterpenes of pomes, emerged as the least investigated. This evidence underscores the need for targeted research to address knowledge gaps and fully leverage the functional potential of these by-products.
Vanacore et al. (Sun,) studied this question.