Studies on digestibility of selected legume carbohydrates and its impact on the pH of the gastrointestinal tract in rats.

Abstract

AbstractA study on the digestibility of legume carbohydrates in unprocessed and processed grain and also in the starch isolated from the grain was carried out by in vitro and in vivo methods. The legumes selected were red gram (Cajanus cajan cv. Hyd. 3A), Bengal gram (Cicer arietinum cv. BEG 482), black gram (Phaseolus mungo cv. T9) and green gram (Phaseolus aureus cv. PS 16). The processes tested were boiling, pressure cooking, roasting, germination, fermentation and parching. The digestibility in vitro was assessed on the basis of maltose released after amylolysis and digestibility in vivo was assessed on the basis of carbohydrate intake and excretion. Digestibilities of the Phaseolus varieties were superior to red gram and Bengal gram. Roasting did not improve the digestibility of any legume as much as boiling and pressure cooking. The digestibility of fermented and germinated legumes was not much higher than the legumes processed by other methods. The increasing order of digestibility in vivo was red gram < Bengal gram < black gram and < green gram. Significant differences were noticed in the digestibility in vivo of moist and dry heat‐treated legumes, and between Phaseolus starches and red gram and Bengal gram starch. The pH values of stomach, duodenum and small intestine contents of rats fed legume diets was greater than the pH values at similar sites in rats fed casein protein, whereas the pH values in the caecum of rats fed on legume diets was acidic and that of casein‐fed rats was neutral. Caecum weight of rats fed on red gram and Bengal gram diets was significantly higher (P<0.05) than black gram‐ and green gram‐fed groups.