Influence of fractions with different molecular weight distributions from high-amylose starches on their digestibility after recrystallization

Type 3 resistant starches (RS3) were prepared from debranched starch (DBS) with different average degree of polymerization (DP) generated from high-amylose pea starch (HAPS) and high-amylose maize starch (HAMS). The results showed that RS3 with DP 35 and DP 39 had the highest RS content (74.5 % and 75.0 %, respectively) after cooking, which were remarkably higher than those of RS3 prepared from mixed fractions (60.6 % and 49.0 %, respectively) and other separated fractions (34.1–63.0 %). The multi-scale structures of RS3, including short-range molecular order, crystalline structure, micro-ordered aggregate structure, microscopic structure, and particle size distribution, were influenced by the average DP. Notably, RS content was positively correlated with the proportion of DP 51–80 and negatively correlated with the proportion of DP 21–30. DBS with DP 51–80 contributed to a more organized micro-ordered aggregate structure at nanometer scale and a larger aggregate structure at micrometer scale, which improved the resistance of RS3 to amylolytic enzymes. However, DBS with DP 21–30 tended to form random coil structure that were more easily to be digested. This research offered new insights into the structure-digestibility relationship of RS3, which is meaningful for the development of RS3 with high resistance to amylolytic enzymes after cooking. [Display omitted] •Gradient ethanol precipitation was utilized to fractionate debranched HAPS and HAMS.•Multi-scale structure and digestibility of cooked RS3 were correlated.•Higher percentage of DP 51–80 led to higher resistance to digestion.•Higher percentage of DP 21–30 contributed to more RDS.•Findings are meaningful for developing RS3 with high resistance after cooking.