Aprovechamiento de subproductos de leguminosas para la obtención de ingredientes funcionalescomparación de metodologías para la caracterización de la fibra alimentaria

Abstract

The large quantities of by-products produced by the food industry present a major problem due to their high volumes and elimination costs. This opens the possibility to reuse these by-products for the obtaining of functional foods. This PhD thesis studies okara, broad bean pod and pea pod, i.e. the industrial by-products from the obtaining of soybean milk, and the processing of broad beans and peas. These by-products have in common that the most important fraction is dietary fibre. Little available information exists about the chemical structures of the structural polysaccharides of the cell wall of these by-products. The knowledge of the structural polysaccharides is necessary to choose the right methods to modify them and to optimise their potential use as functional ingredients. By-products characterization started with a nutritional evaluation, in which emphasis was given to the fat fraction, analysing the fatty acids by gas-liquid chromatography (GLC), and also the mineral content, studying the macro and microelements by atomic absorption spectroscopy (AAS). The okara's fat fraction presents a high content of linoleic acid and contains considerable amounts of oleic and linolenic acids, and so could be a source for these acids, especially for linolenic acid, which hardly appears in many people's dite. In relation to the mineral elements, potassium is the main macroelement, especially in the broad bean pod. The content of calcium is also high, being greatest in pea pod. Iron is the main microelement, especially in pea pod. Okara and pea pod present a considerable amount of manganese, and zinc is an important microelement in okara. Low molecular weight carbohydrates (LMWC) were analysed by HPLC, using two widely used columns to analyse carbohydrates, HPX-87P (Bio Rad) and Carbohydrate Analysis (Waters). LMWC were in greater amounts in soybean than in its by-product okara and even greater in broad bean and pea pods. Mono- and disaccharides showed similar values using both columns; however, oligosaccharides have higher values using the HPX-87P (Bio Rad). The most important LMWC in the broad bean and pea pods were glucose and sucrose ; in okara, the main ones were ?-galactosides, raffinose and stachyose, and arabinose...