小麦后熟期间关键糖组分动态积累规律及其酶促调控机理研究

The quality of wheat could not be improved until 3-6 months of physiological process after harvest. Exploring the mechanism and regulation of wheat after-ripening is important for shortening the storage period and improving the quality of wheat. Researches about after-ripening of wheat is always focused on wheat flour qulaity during storage, however, carbohydrate, one of the most important component of wheat, has not fully found. In this research, the content of carbohydrates in wheat grains were evaluated by glycomics methods such as HPLC and Fluorescence-assisted carbohydrate electrophoresis, et al. Then, the key reducing sugars and non-reducing sugars were confirmed in order to reveal the relation of the key carbohydrates and wheat flour quality. The structure of the key carbohydrates, and its effect on protein structure (eg. the changes in redox state and crosslinking state of glutein and prolamin) was studied by infrared spectroscopy and mass spectrometry, in order to reveal the relation of dynamic accumulation of key sugars and supramolecular structure of protein. The change of enzyme (eg. sugar-based invertase) activity in wheat during storage was evaluated by enzyme engineering technology, and its effect on glycometabolism were studied in order to explore the process of glycometabolism. It could provide a theoretical exploration for the regulation of the stored wheat.

后熟是小麦收获后继续的生理过程，在为期3-6个月的后熟期内小麦因品质低下而无法有效利用。探讨后熟进程机理并调控以实现其缩短具有重要意义。目前后熟作用对小麦粉品质影响方面有一定研究，而对后熟期间关键糖组分动态积累规律及其酶促调控机理的研究较少。本课题以新收获小麦为研究对象，以糖代谢组学及相关研究方法为基础，利用高效液相色谱和荧光辅助糖电泳等手段研究小麦后熟期糖组分含量变化规律，分析关键还原糖和非还原糖成分,揭示关键糖组分与小麦粉品质的关系；利用红外光谱和质谱解析等方法研究后熟过程关键糖组分结构变化特征及其对蛋白结构（如谷蛋白和醇溶蛋白氧化还原及交联状态）的影响，揭示关键糖组分积累规律及其与蛋白质超分子结构的关系；借助酶工程技术研究小麦后熟过程酶（如糖基转化酶）活性变化对糖类代谢控制作用，揭示酶促调控关键糖代谢进程的机理。该研究可为调控小麦后熟时间提供理论探索。

为探明小麦在后熟期间主要糖组分变化规律及酶促调控机制，本研究选取三种不同筋力的新收获小麦籽粒，研究后熟期间小麦籽粒的容重、籽粒特性、蛋白含量、加工特性、小麦粉品质变化以及关键糖组分含量和结构的变化，并进行相关性分析。主要研究结果如下：.不同筋力小麦籽粒随后熟时间的延长，籽粒容重总体呈下降趋势；籽粒平均重量和粒径变化基本一致；籽粒的粗蛋白含量变化不显著；加工特性和小麦粉品质得到优化：出粉率升高，α-淀粉酶活性降低，沉降值升高，面筋指数增加。在后熟过程中，研究所用高筋和低筋小麦籽粒的角质率下降、粉质胚乳所占比例增大，而中筋小麦籽粒此变化不明显。 . 不同筋力小麦籽粒随后熟时间的变化，其制得小麦粉的吸水率、耐搅拌稳定性均有不同程度的差异：RVA曲线中峰值粘度、衰减值、糊化温度整体呈下降趋势，峰值时间增加；拉伸面积、拉伸阻力、最大拉伸阻力、拉伸比例和最大拉伸比均呈上升趋势，延伸度呈下降趋势。随着后熟时间的延长，不同筋力小麦粉制得面团均表现出弹性模量升高、抗形变能力增强，韧性增强。. 不同筋力小麦籽粒后熟期间粗淀粉含量整体略微下降，其中直链淀粉含量在储藏前期（15-60天）呈上升态势，至120天后稳定，支链淀粉含量整个储藏过程中持续波动；损伤淀粉含量持续下降趋势至储藏90天后达到稳定；高筋小麦的淀粉结晶度随储藏时间而下降至90天左右稳定，中低筋小麦淀粉则变化不大；高筋小麦A 淀粉结晶度随储藏时间增加而上升至120天达到最大，中筋小麦中于储藏前期呈上升趋势，90天时略有下降，后趋于稳定，低筋则无明显变化；A、B淀粉XRD谱图在整个后熟过程中均无明显变化。 . 相关性分析得出：新收获小麦籽粒的储藏时间与小麦的籽粒特性、加工特性、α-淀粉酶活性、小麦粉糊化特性、粉质特性、可溶性糖含量、木聚糖含量、破损淀粉含量、以及相关糖组分的含量和结构均相关，程度不一。该研究揭示新小麦后熟期间关键糖组分动态积累规律，阐明糖代谢进程对小麦后熟的影响。