阿拉伯胶改良全麦烘焙制品品质的机理研究

In our previous study, the main factor of restricting the baking quality of whole-wheat product was the water competition and migration between arabinoxylans and gluten network in whole-wheat dough system which led to its inferior baking volume. Besides, Arabic gum can improve the baking volume of whole-wheat product significantly. In this project, the interaction between Arabic gum and components in whole-wheat dough system will be studied. The effect of Arabic gum on rheological properties, changing of particle size, changing of microstructure, the interaction groups and sits of components in whole-wheat dough system will be discussed. Besides, the effect of Arabic gum on water migration and redistribution between the Arabic gum and arabinoxylans and gluten-starch complex in whole-wheat dough system, respectively will be studied by low-field NMR. In addition, the molecular dynamics simulation method will be adopted to discuss the key scientific problem of revealing the mechanism of improving the quality of whole-wheat product by the Arabic gum, also the theoretical and scientific basis will be provided for realizing the goal of improving the quality of whole-wheat product in the future.

前期研究发现，全麦面团体系中阿拉伯木聚糖与小麦面筋蛋白之间存在竞争性吸水及其引发的水分迁移现象是影响全麦制品尤其是全麦烘焙制品品质的最主要原因，且发现阿拉伯胶对全麦烘焙制品品质尤其是烘焙体积具有显著的改善作用。本项目拟对阿拉伯胶与全麦体系中各组分的相互作用开展研究，通过分析阿拉伯胶对全麦面团体系中各组分流变学特性、结合粒子大小变化、微观结构改变以及相互作用基团和位点等的影响，重点探讨阿拉伯胶分别与全麦面团体系中阿拉伯木聚糖和小麦面筋蛋白-淀粉复合物之间的相互作用关系，并利用低场核磁技术从水分迁移及重新分布角度揭示阿拉伯胶改善全麦烘焙制品食用品质的作用机制这一关键科学问题。同时结合分子动力学模拟的研究方法，进一步从分子水平辅助验证阿拉伯胶对全麦制品的改良机理，并为今后实现全麦制品品质的改良目标提供理论基础和科学依据。

为了揭示阿拉伯胶对全麦烘焙制品品质提升的机理，明确阿拉伯胶与阿拉伯木聚糖和小麦面筋蛋白-淀粉复合物之间的相互作用关系，本项目通过研究全麦体系中阿拉伯木聚糖与小麦面筋蛋白-淀粉复合体系以及阿拉伯胶之间的流变学特性、微观结构特征、糊化特性、热力学稳定性和体系内水分分布及迁移等，并利用分子模拟软件对阿拉伯胶与阿拉伯木聚糖之间的相互作用关系（包括：结合位点、关键残基、作用力类型、CDOCKER能、分子间氢键、氢键键长以及氢键键角等）进行模拟，进而预测分子间最佳的结合模式。实验结果表明，阿拉伯胶可降低小麦淀粉的粘度值和回生值，抑制淀粉破损率并提高了其热稳定性。经小角散射实验证明，阿拉伯胶的加入扩大了淀粉的有序结构峰，表明阿拉伯胶与淀粉发生了相互作用关系，但该复合结构为热力学不稳定结构。阿拉伯胶改善了小麦面筋蛋白-淀粉复合体系的粘弹性，这可能是由于阿拉伯胶具有较强的亲水性，使得全麦体系中的水分向小麦面筋蛋白-淀粉复合体系中迁移，小麦面筋蛋白得以充分吸水形成网状结构，进而改善了全麦烘焙制品的品质。通过低场核磁实验对小麦面筋蛋白-淀粉复合体系的T2弛豫时间分布也证明了，阿拉伯胶的加入促使体系中的水分逐渐向小麦面筋蛋白-淀粉复合物体系中迁移。经分子模拟分析，阿拉伯胶与阿拉伯木聚糖主要的相互作用位点为阿拉伯胶中氨基酸残基羟脯胺酸和丝氨酸与阿拉伯木聚糖的(1→3,1→4)木糖主链和阿拉伯糖侧链的多糖残基发生范德华相互作用而结合，少数多糖残基与其发生静电相互作用。糖苷键以1→4连接的木糖分子与阿拉伯胶在活性位点3上比1→3连接的木糖分子有亲和力，阿拉伯糖的双糖分子糖苷键以1→2连接时，在活性位点5上与阿拉伯胶所形成的复合物最稳定。这也表明糖苷键的连接类型对活性位点与多糖的分子对接有一定的影响。