On the nutritional properties of starch and dietary fiber in cassava bread
1989
Tovar, J. | Bjorck, I. | Asp, N.G.
Soluble fiber accounted for 40% of the total dietary fiber content in cassava bread. The soluble fraction consisted of mainly uronic acid and glucose polymers (pectins and beta-glucans), whereas the insoluble fraction was rich in cellulose and lignin. Cassava bread starch showed a high degree of gelatinization (97%) and was completely hydrolyzed by microbial alpha-amylase / amyloglucosidase treatment. Its rate of hydrolysis at moderate concentrations of pancreatic alpha-amylase was, however, slower than that observed for boiled wheat starch. This difference did not persist after pepsin pre-digestion of cassava bread. An isolated total dietary fiber fraction from cassava bread, as well as guar gum, decreased the release of starch digestion products from dialysis tubings. Either material also lowered the rate of gastric emptying in rats. These results suggest two reasons for the low in vitro Digestibility Index previously reported for cassava bread: a limited starch availability due to starch-protein interactions, and fiber-related changes in the viscosity of the medium. This feature, besides the observed retardation of gastric emptying caused by its fiber constituents, makes cassava bread an interesting product to be tested for its in vivo glycaemic response.
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