Encapsulated amylosucrase-treated starch with enhanced thermal stability: Preparation and susceptibility to digestion

Understanding in vitro digestibility and release experiments with starch-entrapped calcium alginate microspheres provide the possibility of controlling starch digestibility in the human gastrointestinal tract. Native and amylosucrase (AS)-treated waxy corn starches (5000U, 20000U, and control) were encapsulated with three different ratios of sodium alginate: 0.5, 0.7, and 1.0%. The slowly digestible and RS fractions of the encapsulated starch were 57.5 and 97.7%, respectively. After cooking, the proportions of these fractions still ranged from 55.7 to 96.1%, depending on the type of starch and concentration of sodium alginate, whereas the un-encapsulated starch contained between 2.9 and 48.3% slowly digestible and RS after cooking. In vitro release was studied in both uncooked and cooked encapsulated samples. When incubated in simulated gastric fluid, the beads swelled and started to float but did not erode, even after thermal treatment. Incubation in simulated intestinal and colonic fluids caused the beads to release starch in both uncooked and cooked starch-encapsulated samples. Encapsulated AS control and native waxy corn starch samples released much more starch than AS-modified starches. The total amount of starch released did not exceed 20% for uncooked samples and 25% for cooked samples.