Oligosaccharides in raw and processed legumes

Abstract

 Oligosaccharides from several types of raw and processed legume seeds consumed in Spain, e.g. lentils (Lens culinaris L.), chickpeas (Cicer arietinum L.), red kidney beans (Phaseolus vulgaris L.), white common beans (Phaseolus vulgaris L.), “Judiones de la Granja” great white beans (Phaseolus vulgaris L.) and faba beans (Vicia faba L.), were analysed by high performance liquid chromatography. The total sugar content ranged from 6.69% to 9.99%, and oligosaccharides represented 25–46% of the total sugar, in the various dry legumes. The main oligosaccharide in raw faba beans was verbascose (3.32%), and stachyose in the remaining legumes (2.21–3.23%). Different amounts of sucrose and traces of glucose, fructose and small amounts of inulin were present in raw samples of all the legumes. After soaking in tap water the loss of oligosaccharides was lowest in red beans (1.25%) and highest in common white beans (27.6%). Pressure cooking, without previous soaking, resulted in no oligosaccharide loss in common white beans but a loss of up to 32% in chickpeas. After pressure cooking of soaked legumes, the loss of stachyose ranged from 14.2% in red beans up to 35.9% for lentils. Substantial amounts of flatus-producing factors can be eliminated by common processing methods.