Lopez-Rubio Amparo, Htoon Aung, Gilbert Elliot P
Bragg Institute, Australian Nuclear Science and Technology Organization, PMB 1, Menai, NSW 2234, Australia.
Biomacromolecules. 2007 May;8(5):1564-72. doi: 10.1021/bm061124s. Epub 2007 Mar 30.
An in-depth characterization of the structural changes undergone by high-amylose starch after extrusion and digestion with a pancreatic alpha-amylase has been carried out. The combination of USAXS, SAXS, XRD, and SEM techniques has provided a wide "picture" of the morphological transformations of starch, covering a length scale from approximately 0.3 nm to approximately 230 microm. Depending on the extrusion conditions, either gelatinization was attained ("mild" conditions) or single-amylose helix formation was induced ("extreme" conditions). SAXS experiments demonstrated that upon contacting the extruded materials with water, retrogradation took place. A new type of molecular organization with a characteristic repeat length of 5 nm was observed in the dry resistant starch fractions from the extruded high-amylose starch. The crystalline morphology of the resistant starch fractions, as observed by XRD, varied from B-type crystallinity for the "mild" extruded starch to a mixture of C- and V-type crystallinity in the case of "extreme" extrusion.
对高直链淀粉在挤压以及用胰腺α-淀粉酶消化后所经历的结构变化进行了深入表征。小角X射线散射（USAXS）、小角X射线散射（SAXS）、X射线衍射（XRD）和扫描电子显微镜（SEM）技术的结合提供了淀粉形态转变的广泛“图景”，涵盖了从约0.3纳米到约230微米的长度尺度。根据挤压条件，要么实现了糊化（“温和”条件），要么诱导形成了单直链淀粉螺旋（“极端”条件）。SAXS实验表明，将挤压材料与水接触后会发生回生。在挤压高直链淀粉的抗消化淀粉级分中观察到一种新型分子组织，其特征重复长度为5纳米。通过XRD观察到，抗消化淀粉级分的晶体形态从“温和”挤压淀粉的B型结晶度变化到“极端”挤压情况下的C型和V型结晶度的混合物。
