Junyu Tang,Jianwei Zhou,Xinyue Zhou,Dandan Li,Zhengzong Wu,Jinhu Tian,Enbo Xu,Donghong Liu
Resistant starch (RS) is widely used as a new type of dietary fiber, but it is still a limitation of controllable formation of microstructure and polymeric architecture for preparing single-component RS (pure-phase). In this study, RS was prepared using maize starch with two ratios of amylose to amylopectin (RAA 1:1 and RAA 1:2 ) and four pullulanase concentrations (5, 15, 25, 35 U/g) in a high-solid dynamic reaction environment of bio-extrusion. Based on the long- and short-range orders reflected by the glycosidic bonds ( 13 C NMR), chain-length distributions (SEC/FACE), single-/double-helices (FTIR), lamellas (SAXS) and crystalline pattern (XRD), the rearranged supramolecular structure of starch and their relationships with physicochemical properties (DSC and RVA) was illuminated. There were two morphologies of RS were created: 1) disordered fusion-like structure displayed by RAA 1:1 -P15 and RAA 1:2 -P35, which had the high contents of RS (54.95 and 54.19%) and short amylopectin (DP ≤ 24) (70.52% and 60.20%). The short (A chains) and extremely short (DP < 6) amylopectin could contribute to form submicro-crystallite with B1 chains in the extruded matrix at a low moisture level; 2) thinner, scalier and layered-like structure displayed by RAA 1:2 -P15 that was the transition state from thick layered strips of large granules. Its SDS content was high (33.61%) and owned the larger rearranged d Lorentz (16.97 nm). Overall, the entangled regime of amylose and amylopectin in the modifications of starch with different structural units or micro-domains in this study will provide a new idea and reference to explore the preparation of novel RS.
Starch chain-length distributions play a key role in regulating the processing and digestion characteristics of proso millet starch. Waxy proso millet starch has higher endothermic enthalpy (13.06–16.73 J/g) owing to its higher relative crystallinity (27.83%–32.04%), while nonwaxy proso millet starch has lower peak viscosity (1.0630–1.1930 Pa∙s) and stronger viscoelasticity owing to its higher amylose content (21.72%–24.34%). Non-waxy proso millet starch exhibited two different digestion phases and its resistant starch content (18.37%–20.80%) was higher than waxy proso millet starch. Correlation analysis showed proso millet starch with longer amylopectin B1 chains and more amylopectin B2 chains exhibited excellent thermal ability and retrograde resistance, whereas proso millet starch with shorter and more amylose medium/long-chains not only reduced the digestion rate and increased the resistant starch content but also exhibited stronger viscoelasticity and excellent retrogradation properties. These results could provide more insights into efficient utilization of proso millet starch.
危险品化学品经营许可证（带存储）