Enhancement of enzymatic resistance in V-type starch inclusion complexes by hydrothermal treatments

Resistant starch (RS) is well known for its health beneficial effects for glycemic control and gut health. In addition to some commonly reported RS types, such as raw high amylose maize starch (HAMS), potato starch, retrograded starch, and cross-linked starch, formation of starch inclusion complexes could also contribute to an increase in RS content. In this study, V type starch inclusion complexes with two guest compounds, ascorbyl palmitate (AP) and palmitic acid (PA), were formed using the novel “empty” V type method, and hydrothermal treatments were performed to further enhance the RS contents. Complimentary X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques were conducted to assess the crystalline structure and thermal properties of the raw and treated inclusion complexes, and simulated in vitro enzymatic digestion was performed to study the structure-digestibility relationship in the treated samples. Although the raw inclusion complex samples exhibited minimal RS contents, all the treatments retarded starch digestion by increasing RS or SDS levels. For both V6h-AP and V6h-PA inclusion complexes, annealing followed by long-term strong acid hydrolysis treatment (ANN-ACH) resulted in the greatest increase in RS content, followed by strong ACH treatments alone. In addition, while presenting a comparable RS level as traditional RS2, the ANN-ACH treated V6h-AP inclusion complex retained a V type crystalline structure, indicating its great potential as a novel type of RS, i.e., RS5. The study findings could have practical implications for the design and modification of RS-containing food for the control and modulation of glycemic response.