Insights into the relation between multi-scale structure and in-vitro digestibility of type 3 resistant starches prepared from wrinkled pea starches

Type 3 resistant starch (RS3) was prepared using acid thinning, gelatinizing, debranching, and recrystallization from wrinkled pea starches (79.5%–94.4% amylose content), and then the structure was further modified by heat-moisture treatment (HMT). Longwan 7 RS3 after pressure heating treatment (PHT) with 30% moisture showed the highest RS content (84.7%). The effect of modification on in vitro digestibility of wrinkled pea RS3 was investigated from the view of multi-scale structure variation. For short-range ordered structure, the modification decreased the proportion of single helix and random coil, and increased the proportion of double helix. The relative crystallinity was enhanced after modification and it showed significant positive correlation with RS content. At longer scale, the modification destroyed the lamella structure and induced the formation of ordered aggregate at nanometer scale. The starch particles also gathered to form aggregate at micrometer scale. The improved double helix proportion, relative crystallinity, size of ordered aggregate at nanometer scale and size of aggregated particles at micrometer scale favored the resistance to enzymatic hydrolysis of wrinkled pea RS3. The present study advanced our understanding of how structure modification influenced in-vitro digestibility of wrinkled pea RS3, which is meaningful for the development of high quality RS3.