A STUDY ON THE IN-VIVO DIGESTIBILITY OF RETROGRADED STARCH

The digestibility of different forms of starch was examined in an ileo stomy model. Six otherwise healthy ileostomists were fed a controlled polysaccharide-free diet for four days, on three of which a test starc h was added at breakfast. 50 g starch was fed as either whole or homog enized chick peas or as a retrograded starch gel. A readily digestible wheat starch biscuit was used as a control. Ileostomy effluent was co llected every 2 hours over a 16 hour period and a final collection mad e at 24 hours after the test meal. The monosaccharide composition and glycosyl linkages of the residual carbohydrate in the 2 hour peak peri od following the test meal was determined. Following consumption of th e starch gel, poly- and oligosaccharides from mucin and starch were id entified in the effluent. At the peak of effluent production following the test meal, the average ratio of starch polysaccharide to mucin wa s 1:0.4. Of the 50 g of starch consumed, 7% of the starch escaped dige stion in this fraction. Following consumption of cooked, cooled chick peas, which were fed whole or homogenized, polysaccharides deriving fr om starch, mucin and the cell wall were detected in the effluent. It w as estimated from comparison of the composition of the food and efflue nt that 14% and 16% of the ingested starch in the form of homogenized and whole chick peas had escaped digestion in the small intestine. Lin kage analysis showed the chemical structure of the starch escaping dig estion after feeding the whole and homogenized chick peas was similar to that obtained after feeding the starch gel. Copyright (C) 1996 Else vier Science Ltd