Varying amylose contents affect the structural and physicochemical characteristics of starch in mung bean

Abstract

Mung bean starches are widely used for producing transparent, good-quality noodles in the food industry. This study isolated starches from eight mung bean varieties and investigated how the amylose contents (19.1–32.9%) of the beans affected the structures, physicochemical properties, and resistant starch (RS) fractions of these starches. The starches were classified into three groups according to their amylose content: low-amylose starches with <25% amylose content (TN182, DXVN7, and DX208 varieties), intermediate-amylose starches with 25%-30% amylose contents (DX14, KPS1, and V123 varieties), and high-amylose starches with >30% amylose contents (T135 and DX044 varieties). The amylose content of mung bean starches negatively correlated with the average degree of polymerization ((Formula presented.)) of the starch, whereas the mung bean variety dictated the average chain length ((Formula presented.), degree of order, and short-range molecular order of the starch. All mung bean starches were found to have an A-type crystalline structure with a relative crystallinity of 25.8–34.7%. The starches with higher amylose contents exhibited higher peaks, final viscosities, and setbacks than the other starches. The contents of the RS fraction were in the range of 3.6–13.0%; the starches of the DX14, T135, and DX044 varieties had higher contents of the RS fractions (9.0%, 9.9%, and 13.0%, respectively) than the starches from the other mung bean varieties. Abbreviations: MB1, starch isolated from TN182 variety; MB2, starch isolated from DXVN7 variety; MB3, starch isolated from DX208 variety; MB4, starch isolated from DX14 variety; MB5, starch isolated from KPS1 variety; MB6, starch isolated from V123 variety; MB7, starch isolated from T135 variety; MB8, starch isolated from DX044 variety.