Introduction

Fruit and vegetable processing (preservation or production of juice, wine, sugar, starch, oil, etc.) generates huge amounts of wastes; in the European Community (EC) approximately 150 million tonnes are produced annually (Awarenet, 2004). Solid waste represents around 30% of the processed vegetables and can reach up to 85% for sugar production from sugar beet. Until recently in Europe, the principal end-use of these wastes was in the animal-feed sector. However, the rules that regulate the world agricultural exchanges jeopardised this market as imported competitive fodder cereals became cheaper and therefore more attractive for cattle breeders. Vegetable wastes are also often spread on land or composted. These wastes have however a high water content and are consequently perishable and micro-biologically instable. This can result in environmental issues such as noxious odours or microbiological hazards. In addition, legislation is strongly encouraging industry to find new end-uses for these by-products. Upgrading these wastes is also of great interest because of its economic profitability, since residues may be available in large quantities at a relatively low cost.

Wastes arising from fruit and vegetable processing industries are rich in cell wall materials. Such plant-derived wastes are generally heterogeneous as they may contain entire vegetable, leaves, stems, roots, tubers, seeds, stones, etc., which makes their upgrading rather difficult. Many plant by-products are still commonly and traditionally used as animal feeds or fertilisers. Some can however provide exploitable products or supplements for the food and other industries (chemicals, cosmetics, pharmaceutics).

Traditional uses include exploitation as sources of hydrocolloids, dietary fibre and ethanol. Nevertheless, for economic as well as environmental reasons, there is a continuous pressure to exploit such residues and to identify products with attractive properties and with potential markets (Laufenberg et al., 2003).

This chapter will consider the upgrading of plant-derived food-processing by-products (mainly vegetable trimmings and residues from extraction). After an inventory of the main origins of the by-products, the upgrading of these plant wastes as a whole, of the constituting polymers, and of the monomeric components, will be addressed.

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