小麦芽水溶性阿拉伯木聚糖的分子溶解机制及其指纹图谱构建

The viscosity of wheat malt and the qualities of wheat beer are affected by the content, composition, structure and property of arabinoxylans (AXs). During the brewing process, especially the malting process, the solubilization mechanism of wheat AXs is still unclear now, which leads to the uneven quality of wheat malt. Therefore, following the change of AXs-degrading enzyme in wheat malt, many analytical instruments including GLC-MS, NMR and rheometer will be used to analyze the molecular weight, average degree of polymerization, xylose to arabinose ratio, the substitution pattern of arabinose units along the main xylan chain backbone, the content and combining pattern of feruloylated groups, rheology and gel properties of water-extractable arabinoxylans (WEAXs). In order to reveal the solubilization mechanism of WEAXs, optimize the malting parameters, construct the fingerprint of structure and characterization of WEAXs in wheat malt, the affecting order of AXs-degrading enzyme on the viscosity of wheat malt, the influencing mechanism of molecular structure, rheology and gel properties, oxidative cross-linking of WEAXs on the viscosity of wheat malt, as well as the degradation kinetics of endogenous AXs enzymes will be discussed together in this project. The implementations of this research would provide theoretical basis for the solubilization and regulation of wheat AXs, which is beneficial to improve the viscosity of wheat malt, solve the brewing problems such as the higher viscosity and filtration difficulty, enhance the productivity and improve the quality of wheat beer. In conclusion, the economic and social benefits will be remarkable.

阿拉伯木聚糖（AXs）的含量组成、结构性质影响小麦芽粘度与小麦啤酒品质。目前啤酒酿造过程，尤其是制麦进程中小麦芽AXs的溶解机制尚无定论，小麦芽质量参差不齐。因此，本课题以小麦芽AXs降解酶的变化为切入点，采用气相液相色谱-质谱联用仪、核磁共振光谱、流变仪等解析小麦芽水溶性阿拉伯木聚糖（WEAXs）的分子量、聚合度、侧链阿拉伯糖数量和取代方式、阿魏酰基团数量与键合方式、流变与凝胶特性等，比较AXs降解酶对小麦芽粘度的影响次序；探讨WEAXs结构特征、流变与凝胶特性、氧化交联对小麦芽粘度的影响机制；研究小麦芽内源AXs酶降解动力学，揭示小麦芽WEAXs的分子溶解机制，优化制麦参数，构建WEAXs结构性质的指纹图谱。本课题研究可为制麦进程中小麦AXs的溶解与调控提供理论依据，改善小麦芽粘度，解决WEAXs引起的麦汁与啤酒粘度高、过滤困难等问题，提高生产效率和小麦啤酒质量，经济与社会效益显著。

阿拉伯木聚糖（AXs）具有粘度高、持水性高等特点。小麦芽中的水溶性阿拉伯木聚糖（WEAXs）易引起麦汁和啤酒粘度升高、浊度增加。本课题以制麦进程中小麦AXs的分子溶解机制研究为主线，通过比较小麦/芽WEAXs的种间差异性，探讨发芽时间和干燥工艺对小麦芽WEAXs理化性质、分子结构特征的影响，识别影响WEAXs分子结构特征的关键制麦参数与降解酶，明确制麦工艺、WEAXs分子特征与小麦芽酿造品质间的构效关系。同时就小麦芽及其小麦啤酒糟（WBSG）的加工、营养功能特性、对小麦面团的改性作用及其在小麦食品中的应用开展广泛研究。.结果表明，制麦和糖化过程中WEAXs的含量增加，A/X值、平均聚合度（avDP）值和分子量（Mw）降低。小麦芽以15310 ~ 24940 Da的WEAXs为主；糖化麦汁以3010 ~ 3820 Da的WEAXs为主。延长发芽时间促进AXs的溶解，麦汁粘度降低。小麦发芽第4 d时木聚糖酶、淀粉酶、葡聚糖酶和阿魏酸酯酶达到最大值。啤酒麦芽制造以发芽4 ~ 6 d为宜。恰当延长55 oC时麦芽干燥的持续时间有利于木聚糖酶活性的保留。小麦芽WEAXs含少量半乳糖，不含甘露糖。小麦芽粘度主要受22940 ~ 29600 Da WEAXs的影响。1300 cm-1 ~ 800 cm-1处的傅里叶红外光谱（FTIR）峰为WEAXs的指纹识别区。小麦面团中小麦芽的推荐添加量为2.5%~5.0%，WBSG的推荐添加量为2.5%~7.5%，二者的极限添加量为10%。.以上研究结果可为制麦进程中小麦AXs的溶解调控提供依据，有利于进一步改善小麦芽品质，提升小麦啤酒质量。将小麦芽、小麦啤酒糟（WBSG）作为食品添加剂应用，实现了小麦啤酒酿造全产业链的食品加工技术优化，经济与社会效益显著，也为进一步研究小麦AXs的食品改性机理提供了思路和参考。