V-amylose Nanocarriers Complexed with Debranched Sweet Potato Starch: Structural Characteristics and Digestibility

V-amylose, consisting of crystal aggregates of nanometric size, is attracting great attention due to its encapsulating capacity utilized as a superior delivery system of bioactive compounds. Debranched starches (DSs) possess remarkable self-assembling properties to enhance the formation of V-amylose, but the effect of debranching degree on the conformational properties of the DSs has yet systematically investigated. In this study, the molecular structural characteristics of the DSs with different debranching degrees and their complexing ability with lauric acid (LA) and in vitro digestibility were investigated. The DSs displayed a broad/trimodal molecular weight (MW) distribution and comprised three types of glucan molecules with different degrees of polymerization (DP). The proportions of chains with DP 19–22 and 49–67 in the DSs increased with increasing debranching degree, while the proportion of chains with DP 1554–4252 decreased. The complexing indices were positively associated with the debranching degree. A combination of V- and B-type polymorphs with increased crystallinity were detected in the DSs-LA mixtures compared to their native counterpart, reflecting the formation of crystalline structures of single-helical V-amylose and amylose double helices. The crystallinities were facilitated by the effect of the DSs and were strongly related to the increased resistance to digestion. These results can help to elucidate the effect of partially debranched starches on V-amylose formation as a delivery system of bioactive compounds.