Agro-industrial by-products: Valuable sources of bioactive compounds

In a world with eminent scarcity of natural resources and increasing incidence of chronic diseases related to unhealthy eating habits, the search for biologically active and environmentally friendly food products is raising among customers. Agro-industrial by-products have caught special attention from the scientific community for being an available, cost-effective and sustainable source of a wide array of bioactive compounds. Review papers frequently restrain their research to by-products derived from the production of most worldwide consumed crops. Therefore, the aim of this review is to summarize the latest overall research, which focus on the biological potential of agro-industrial by-products and their bioactive compound profile, targeting their application as food ingredients, including not only researches with worldwide consumed crops, but also local foodstuff. A total of 152 research papers, browsed in 2 databases, and involving more than 30 countries were gathered. The richness of bioactive compounds of food by-products from different industries, from fruits to marine products, is ascertained throughout this review. The diversity of food residue being investigated for their nutritional and biological capabilities and the content of specific molecules in each food group are remarkable points. Higher literature reports about fruits by-products may be explained by its wide range of bioactive compounds, especially in Latin American fruits, which includes all flavonoids subclasses, besides betaxanthins, carotenoids and phytosterols. Researchers mainly focus on the quantification of fiber, polyphenols and antioxidant capacity of the investigated by-products, obstructing the investigation of specific biological activities, which are precisely related to the main phytochemicals of the residue matrix, as each molecule has an individual mechanism of action that should be considered when evaluating its biological capabilities. Furthermore, the addition of food by-products has also been advantageous in the production of fortified or enriched bakery, dairy and meat products and functional beverages. All along this literature review, it becomes clearer the high nutritional and nutraceutical value that many by-products possess, besides their attested biological activities, such as antioxidant, anticarcinogenic, antimicrobial, among others.