高压均质对大米淀粉分子结构及体外消化性能的影响

Effect of High-pressure Homogenization on Molecular Structure and in Vitro Digestibility of Rice Starch

摘要:

为了明晰不同高压均质条件对大米淀粉分子结构与消化性能的影响，本研究通过凝胶渗透色谱-多角度激光光散射技术、核磁共振技术和碘比色法考察了均质处理前后大米淀粉分子结构的变化，以及利用体外模拟法比较了高压均质前后大米淀粉的消化性能。研究表明，随着均质压力和均质次数的增加，大米淀粉平均分子量和均方旋转半径均减小，分子量主要分布从5×106~1×107 g/mol和>1×107 g/mol的大分子区域移向1×106~5×106 g/mol和<5×105 g/mol的较小分子区域，表明淀粉分子链发生断裂和降解。α-1,6糖苷键的比例下降说明淀粉分子的支叉结构也受到破坏，直链淀粉含量增加。另外，由于均质过程中直链淀粉与适宜分子量大小的淀粉分子之间易发生重聚集而形成有序的结构域，有利于大米淀粉抗消化性能提高。本研究结果将为利用高压均质技术调控淀粉及淀粉类食品的消化性能和营养功能提供了依据和基础数据。

Abstract:

To clarify the effects of different high-pressure homogenization (HPH) conditions on the molecular structure and digestibility of rice starch, the changes in the molecular structure of the rice starch before and after HPH were evaluated by gel permeation chromatography-multi-angle laser light scattering, nuclear magnetic resonance spectroscopy and iodine colorimetry in this study. Comparison was made on the digestibility of native and HPH-treated rice starch following in vitro simulation. The results showed that with the increase of homogenization pressure and cycles, both the average molecular weight and mean square rotation radius decreased, with the main molecular weight distribution shifting from the high-molecular weight region (5×106~1×107 g/mol and >1×107 g/mol) towards the low-molecular weight region (1×106~5×106 g/mol and<5×105 g/mol). These results indicated the breakdown and degradation of starch molecular chains. The decrease in the proportion of the α-1,6 linkages suggested the damage of the branched structure of starch, causing the increase of amylose content. In addition, an ordered domain was formed due to the re-aggregation between amylose and the starch molecules with appropriate molecular weights during HPH, which facilitated the increase of resistance to digestion for the rice starch. The results of this study will provide a foundation and fundamental data for regulating the digestibility and nutritional functions of starch and starchy foods through HPH.