In the present study, starch extrudates with varying moisture contents (30%, 40%, and 50%) were prepared by twin-screw extrusion; the morphology, structural order changes, in vitro digestion, and fecal fermentation characteristics were investigated. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses demonstrated the extrusion process severely disrupted the starch order, while the addition of water reduced this disruptive effect. The long-range ordered structure of starch extrudates gradually decreased with the increasing moisture contents, indicating the damage degree of starch extrudates increased with increasing moisture content. Compared to high maize 260 (NS), extruded starch (ES) and starch extrudates with different moisture contents (S-30, S-40, and S-50) exhibited a significantly higher hydrolysis rate, digestion extent, and fermentation rate, while no significant differences were shown among starch extrudates with different moisture contents. Interestingly, compared to ES, starch extrudates with high moisture contents (S-30, S-40, and S-50) exhibited significant higher levels of short-chain fatty acids (SCFAs). Pearson correlation analysis showed the yields of SCFAs were positively correlated with the content of V-type starch formed during extrusion. These findings provide a theoretical guidance for the design of starch-based extruded foods with varying moisture contents.
Zhang et al. (Mon,) studied this question.