Structures and digestibility of B-type high-amylose rice starches compared with A-type high-amylose rice starches

Abstract

The starch structures and digestibility of starches prepared from newly developed Korean high amylose rice varieties were investigated. Amylose (AM) contents of Goami, Shingil, Goami 2, and Dodam starches were 25.56, 30.34, 36.33, and 45.78%, respectively. The Goami and Shingil starches were A-type crystallinity, while the Goami 2 and Dodam starches were B-type crystallinity. The molecular weights of AM were lower in the B-type starches (1.64 × 105 and 1.88 × 105) than in the A-type starches (3.88 × 105 and 3.00 × 105). The average chain length (CL) and longer branch CL (DP ≥ 25) of amylopectin (AP) were higher in B-type rice starches than in A-type rice starches. The ratio of 1045/1022 cm-1 and relative crystallinity were lower in the B-type rice starches. These results show that B-type starches have a higher AM content (>35%), gelatinization temperature, resistance to digestibility, and longer branch CL of AP, but a lower AM molecular weight than A-type starches.