Résumé
The grapefruit is one of the most produced and consumed citrus fruits in the world, with an average annual production of 7 million tonnes. It has become increasingly popular, as it is considered a low-calorie fruit, rich in vitamins, minerals and many other valuable nutrients (flavonoids, carotenoids, essential oils…). Over half a million tonnes of grapefruit undergo processing, mainly into juice, which generates large amounts of wastes (peel, seeds, pulp and leftover membrane), since only 50% of the fruit is used in this manufacturing process. Today, these wastes are mostly discarded or used as cattle feed. These practices are unfortunate, as grapefruit processing wastes could be a source of high-added economic value. Indeed, they represent a source of dietary fibers, sugars, essential oils, flavonoids and carotenoids, valuable in various industrial sectors (energetic, agricultural, pharmaceutical, cosmetic and food). Thus, if grapefruit wastes can be used to produce biogas or bio-energy, to fertilize soil or as biosorbent in wastewater treatment, the recovery of their bioactive compounds (e.g. pectin, essential oils, carotenoids and flavonoids) could be also highly pertinent, as these compounds present a wide spectrum of technological properties and/or health benefits. Extraction processes usually adopted to recover those compounds use organic solvents, high temperatures and long extraction times, which are considered to generate a high environmental impact. As a result, in recent decades, different operating strategies have been developed (ultrasound-, microwave-, pulsed electric field-assisted extraction, and supercritical fluids), with the objective of increasing extraction yields while reducing use of resources. However, most of them have still economic or technological limitations that prevent their development in small and medium-sized enterprises. The present chapter expands on the aforementioned aspects of grapefruit wastes, with the objective of demonstrating their high re-use potential. This chapter presents the potential valorization of grapefruit wastes in food and non-food applications and offers a brief overview of the main emergent extraction technologies.