湿热处理对大米淀粉多层次结构及消化特性的影响

为了明晰湿热处理前后大米淀粉多层次结构与消化性能之间的关系，本研究采用体外模拟法测定湿热处理前后大米淀粉的消化性能，并通过小角X射线散射（SAXS）、X射线衍射（XRD）和凝胶渗透色谱-多角度激光光散射（GPC-MALS）等现代分析技术考察湿热处理前后大米淀粉不同层次结构的变化。研究表明，湿热处理可引起大米淀粉半结晶片层的有序化程度下降，降低其结晶程度和分子量；同时，伴随着淀粉颗粒内部层状、结晶及分子链结构的破坏，淀粉-脂质复合物的形成及Mw >2×107 g/mol的高分子量片段的降低和Mw<5×106 g/mol的低分子量片段比例的增加（0%增至21.3%）有利于大米淀粉慢消化和抗消化性能的提高，而当Mw<5×106 g/mol比例增至32.1%时，可能由于低分子量片段较多，反而阻碍了慢消化和抗消化性能的提高。研究结果为湿热处理加工技术调控淀粉及淀粉质食品的消化性能提供了理论支撑和基础数据。
To understand the relationship between the multi-scale structures of rice starch and its digestibility before and after heat-moisture treatment (HMT), the digestibility levels of rice starch before and after HMT were determined by in vitro simulation HMT-induced alterations in the multi-scale structures of rice starch were evaluated by small-angle X-ray scattering, X-ray diffraction, and gel permeation chromatography coupled with multi-angle light scattering. The study showed that the degree of the semi-crystalline lamellae order, relative crystallinity, and molecular weight of rice starch were reduced by HMT. Additionally, damage to the crystalline, lamellar, and chain structures inside the starch granules, formation of V amylose-lipid complex, decreased levels of high-molecular weight (Mw>2×107 g/mol) fragments, and an increased proportion (0% to 21.3%) of low-molecular weight (Mw<5×106 g/mol) fragments favored the formation of slowly digestible starch and resistant starch.. However, when the proportion of the starch fragment with Mw<5×106 g/mol was increased to 32.1%, excess low-molecular weight fragments lead to the formation of rapidly digestible starch. The results provide a theoretical basis and basic data for the adjustment and control of the digestibility of novel functional starch and/or starchy products by using HMT.