Large scale isolation of water-soluble and water-insoluble pentosans from wheat flour

A procedure has been developed which allows the isolation of enriched pentosan fractions from wheat flour. The procedure is based on mixing flour and water (50 kg/150L). After centrifugation the supernatant is heat-treated and then concentrated by cross-flow ultrafiltration to give water-soluble pentosans, whereas the insoluble residue is treated with Alcalase and then Termamyl to give water-insoluble pentosans. Starting from 50 kg of flour from three different varieties (Soissons, Thésée, Apollo), water-soluble and water-insoluble pentosans containing respectively 100–200 g of water-soluble and 250–350 g of water-insoluble arabinoxylans, were prepared within 2 d. Water-soluble pentosans are constituted of approx. 40% arabinoxylans and are contaminated by proteins, whereas water-insoluble pentosans are composed of arabinoxylans (ca. 30%) and are contaminated by residual starch (ca 40%). Enrichment factors in arabinoxylans ranged from 98 to 66 for water-soluble and 27 to 19 for water-insoluble pentosans as compared with initial flour.