交联剂对大豆蛋白冻胶的影响

Physical gels are three dimensional networks made of macromolecules via physical interaction, such as hydrogen or ionic bonding and hydrophobic interaction, with a large amount of encapsulated solvent. As a kind of soft materials, they can remain its shape under gravity, behaving like a solid; but deform and flow under a relatively small external force, acting as a liquid. “How to quantitatively study their gelation processes and mechanical properties without any disturbance or with a micro-disturbance?” has troubled macromolecular network researchers. In this project, we will study the gelation kinetics, the sol composition, the sol-gel ratio and the gel viscoelasticity at the molecular and microscopic levels via a combination of laser light scattering, analytical ultracentrifuge, photo-bleaching-and-recovery spectroscopy, and magnetic tweezer single particle micro-rheology. Since soy proteins have a wide range of applications in food, pharmaceutical and cosmetic productions, we will focus our study on effects of type, concentration and adding method of cross-linking agents on the formation of physical gels made of water-soluble -conglycinin and their mechanical properties. Besides traditional inorganic salts, we will specially search for effects of various cationic polysaccharides gelling-flocculating agents on physical gels. This applied basic research not only enables us to have profound understanding of molecular mechanism of -conglycinin gel formation and provide novel quantitative methods for physical gel study, but also improve relevant processes and products.

冻胶是大分子通过氢键、离子键和疏水等物理作用形成的含大量溶剂的三维交联网络。作为一种软物质，其在重力下，可保持形状，似固体；但在较小的附加外力下，便会形变和破碎，又似液体。“如何在无扰或微扰下,定量地研究其成胶过程和力学性能？”一直困扰着大分子网络的研究者。在本项目中，我们提出将激光光散射、分析型超速离心仪、荧光漂白恢复光谱和磁镊单粒子微流变仪结合起来，在分子和微观水平上研究成胶动力学、溶胶成分、溶胶-冻胶比例、以及冻胶的粘弹性。由于大豆蛋白在食品、药品、化妆品等方面具有广泛的应用，我们将侧重研究交联剂的种类、浓度和加入方式对水溶性β-伴大豆球蛋白冻胶的形成和力学性能的影响。除了传统的无机盐外，我们将特别探索不同的阳离子多糖大分子交联-凝絮剂对冻胶的影响。该项应用基础研究使得我们不仅可深入了解大豆蛋白冻胶形成的分子机理以及提供研究冻胶的新型定量方法，而且还能优化相关的工艺和产品。

本项目研究了多价阳离子多糖交联作用下大豆蛋白形成冻胶的微观过程及影响因素，并开发了一个新型大豆蛋白冻胶的生产工艺。我们利用动态激光光散射在分子水平上研究β -伴大豆球蛋白在壳聚糖的加入过程中的聚集、交联和微凝胶形成，发现球蛋白复合体的粒径增长速度与壳聚糖聚合度呈正相关。聚合度大于四才能有效交联蛋白，聚合度大于十则可以利用更少的阳离子多糖（蛋白质量的1-2%）实现交联，这体现了多糖大分子链上多个阳离子的协同交联作用。对比传统工艺使用的二价氯化镁，相同质量的壳聚糖在适当的加入方式下，可以形成更具韧性的老豆腐；基于此，我们开发了新型多糖豆腐的生产工艺与产品。交联剂对蛋白冻胶的影响与蛋白质的多肽链组成密切相关，不同多肽链因带电特性与亲疏水性的差异，在成胶过程中产生不同的静电与疏水相互作用。为此，我们开发了一个基于离子交换-反相二维液相色谱的定量分析方法，用于剖析带电特性和亲疏水性两个维度上的大豆蛋白多肽链组成。我们解析了中国境内不同大豆品种的成冻胶特性，建立了品种-蛋白特性数据库，为豆制品行业提供技术支持。