Fate of U-C-14-gelatinized and U-C-14-retrograded bean starch in the rat

The fate of retrograded and gelatinized bean starch in the rat was followed using an in vivo radiolabel technique. [U-C-14]Bean starch was obtained by incubating excised unripe pods of broad beans with (CO2)-C-14. After extraction and purification, [C-14]bean starch was either retrograded or gelatinized and fed to rats by gavage. Rats were housed individually in metabolic cages and were given free access to food and water. After 3 and 18 h of gavage, rats were killed by cervical dislocation and the radioactivity was measured in gut contents, tissues, feces, urine, and CO2. The rate and extent of degradation of [C-14]starch in the small intestine were lower for C-14-retrograded starch, as indicated by the high amounts of alpha-glucans of degree of polymerization >70 in the distal fraction of the small intestine 3 h after gavage. After 18 h of gavage, the percentage of radioactivity present in tissues, feces, and urine was higher in rats fed C-14-retrograded starch. The [C-14]starch degradation products were mainly metabolized by the carcass, pelt, liver and intestinal tissues.