Improving the Resistance to Enzyme Digestion of Rice Debranched Starch via Narrowing Chain Length Distribution Combined with Oven Drying

Abstract

AbstractIn this study, the effects of chain length distribution and drying methods on the structural properties and in vitro digestibility of resistant starch (RS) are investigated. Rice starch is debranched at 10% w/w solid concentrations, incubated at 60 °C, and further subjected to freeze drying and oven drying treatment to obtain debranched starch (DBS). The chain length distribution shows that DBS (the degree of polymerization [DP] = 19.52 ± 0.13) has a high proportion of B1 and B2 chains (DP13‐36) and a narrow chain length distribution. In addition, the results of scanning electron microscopy (SEM) show that the oven‐dried samples have denser structures and larger particle morphology compared to samples prepared by freeze‐drying. In FTIR, LCM‐Raman and X‐ray diffraction patterns, debranched starch supernatant fraction 1 (DBSS1) exhibit higher short‐range molecular order and crystallinity than other samples. Digestibility analysis shows that DBSS1 with narrow chain length distribution (DP13‐36) promotes the high content of RS formation and oven drying is more favorable for RS formation than freeze drying (RSDBSFS1 = 79.69 ± 5.09% and RSDBSOS1 = 84.17 ± 0.17%). This suggests that the proper narrow chain length distribution is conducive to the formation of ordered structure and an increase in resistance. Oven drying provides a larger starch particle size, which facilitates resistance to digestion.