Characterization and In Vivo Hydrolysis of Amylose Stearic Acid Complex

Objectives of this study were to compare thermal properties, swelling power, and enzymatic hydrolysis of a type 5 resistant starch (RS5) with that of normal corn starch (NCS) and high-amylose corn starch (HA7). The RS5 was prepared by complexing debranched HA7 with stearic acid (SA). Because of amylose-helical-complex formation with SA, the RS5 starch granules showed restricted swelling at 95 C. The RS5 displayed a larger RS content (67.8%) than the HA7 (33.5%) and NCS (0.8%), analyzed following AOAC method 991.43 (AACC International Approved Method 32-07.01). When the cooked RS5, HA7, and NCS were used to prepare diets for rats with 55% (w/w) starch content, RS contents of the diets were 33.7, 15.8, and 2.6%, respectively. After the diet was fed to the rats in week 1, approximate to 16% of the starch in the RS5 diet was found in the feces, substantially greater than that of the HA7 diet (approximate to 6%) and NCS diet (0.1%). The percentage of starch not being utilized in the RS5 diet decreased to approximate to 5% in week 9, which could be partially attributed to fermentation of RS5 by gut microflora. Large proportions (68-99%) of the SA in the RS5 diet were unabsorbed and discharged in the rat feces. The results suggest that the interactions between starch and SA can be used to enhance resistance of starch to in vitro and in vivo digestion.