Insights into the regulation mechanisms of dual hydrothermal treatment on the structure and digestive characteristics of A- and B-type wheat starch granules.

Hydrothermal treatment is a physical modification technology to alter starch structures for the production of resistant starch (RS). However, the underlying regulation mechanism of the multiscale structure and digestive properties of starch by dual hydrothermal synergistic treatment remains unclear. To solve this problem, A- and B-type wheat starch granules (AWS and BWS) were separated and subjected to toughening and heat-moisture synergistic treatment (THT) with various moisture content (10 %, 15 %, 20 %, 25 %). Scanning electron microscopy (SEM) and particle size distribution results showed that THT disrupted starch granules and the particles aggregated with each other to increase the particle size. Fourier transform infrared spectroscopy results confirmed that the hydrogen bond between starch molecules was destroyed after THT. Thermogravimetric analysis (TG) results demonstrated that the thermodynamic stability of AWS and BWS was improved after THT. Moreover, THT with 10 % or 15 % moisture content increased the crystallinity of AWS and BWS. The AWS and BWS had the highest RS content with THT at 15 % moisture content (the RS of AWS increased from 17.56 % to 25.04 % and that of BWS increased from 13.03 % to 27.08 %). These results showed that the THT with 10 % or 15 % moisture content improved the regularity of starch molecule accumulation, and promoted the crystalline structure recombination with superior crystallinity, thermodynamic stability, and high enzymatic resistance. Additionally, SEM, TG, particle size distribution, and in vitro digestion results showed that BWS was more sensitive to THT than AWS. This study provides a potential strategy to design functional wheat starchy foods with low digestibility.