Acylated resistant starches: Changes in structural properties during digestion and their fermentation characteristics

Acylated resistant starches have great potential in improving body health due to their special short-chain fatty acids (SCFAs) releasing abilities. The purpose of this study was to investigate the changes in structural properties of acylated starches before and after digestion, and to further reveal their in vitro fermentation characteristics. Acetylated, propionylated, and butyrylated maize starches (MSA, MSP, and MSB, respectively) with similar degrees of substitution (DS) were obtained. The acyl groups were distributed on both the surface and the inner regions of the starch granules. During the digestion, partial acyl groups of MSA, MSP, and MSB were lost, and their DS values decreased from 0.145, 0.164, and 0.185 to 0.066, 0.049, and 0.137, respectively. The average degree of polymerization decreased after acylation and further decreased after digestion, indicating the breakage of the long chains. In the in vitro fermentation stage, acylated starches increased the total SCFAs concentrations when compared to native starch. The introduced acyl groups of the three acylated starches could be effectively released. Moreover, MSP and MSB had more pronounced effect on promoting the release of specific SCFAs than MSA. The current study contributes to understanding the mechanism of functional resistant starch and enriching its applications in functional foods.