In order to preserve them and increase their shelf life, fruits and vegetables are usually canned, frozen or dried. These processes generate around 6 million tonnes of solid waste every year and large quantities of wastewater (3.5-8.5 m3 per tonne of raw material) are also necessary because of specific hygiene and legal constraints. The proportion of waste varies depending on the fruit or vegetable, ranging from 1% of raw material for cranberries to 20-30% for broccoli or carrot. Waste consists essentially of stems, leaves and stalks, which are more often spread on land, composted or used as animal feed. Some vegetable peels have been shown to contain valuable phenolics and bioactive components (Rodriguez et al., 2004; Suutarinen et al., 2004). Fruit stones and kernels are used for natural oils in the food industry, cosmetics or pharmaceuticals. Some leafy by-products (from cauliflower, artichoke, lettuce, chicory, celery, etc.) are rich in dietary fibre (Femenia et al., 1998), carbohydrates (Rupérez and Toledano, 2003, 2004), antioxidants or prebiotics (Llorach et al., 2003, 2004), but their utilisation is still limited (Larrosa et al., 2002).
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