共溶质场中蛋白-多糖共混体系超声增容规律及凝胶形成机理研究

Proteins and polysaccharides were the most important polymer substrate for food gel structure information, and the vast majority industrialized food gel products were prepared through sol-gel transition in co-solute environment. Improving the compatibility of proteins-polysaccharides blends and then arresting the phase separation by gelation is the key method to obtain the expected gel microstructure and optimize its' physical properties such as texture and flavor release etc. Previous study found that ultrasound treatment could form compatibilization effect for protein-polysaccharide blends, while refinement the mixed gel microstructure and improve functional properties. But the phase behavior of proteins-polysaccharidesblends, sonication compatibilization rules and gelation mechanisms remain unclear. Based on these scientific issues, the model proteins-polysaccharides blend system such as gelatin-modified starch and soy protein-konjac gum in co-solute were employed to systematically study the phase behavior, rheological properties, microstructure evolution and the laws of sonication compatibilization rules of proteins-polysaccharides blends using the phase diagram, dynamic rheological testing, laser scanning confocal microstructural tracking and textural analysis technology. The association relationship of phase separation/gelation coupling competition-microstructure- physical properties in co-solute environment would be explored after ultrasound compatibilization proteins-polysaccharides blends. To clarify the mechanism of gel formation sol-gel transition process would be constructed through numerical simulation. This project can provide basis for physical properties design as well as avoidance quality defect food gel products.

蛋白和多糖为构建凝胶食品结构的两最重要高分子基材，绝大多数凝胶食品产品工业化制备成型均于共溶质场中完成溶胶-凝胶转变，通过改善共溶质场中蛋白-多糖的相容性，并利用胶凝固化相分离程度，是实现凝胶食品产品质构、风味控释等物性优化的关键。前期研究发现非共溶质场中超声可增容蛋白-多糖溶液共混体系、细化凝胶微结构并优化功能特性，但共溶质场中蛋白-多糖共混体系相行为、超声增容规律及凝胶机理尚不清楚。基于上述科学问题，拟以明胶-变性淀粉及大豆蛋白-魔芋胶等为模型体系，采用相图、动态流变测试、激光共聚焦微结构跟踪及质构分析等技术，系统研究共溶质场中蛋白-多糖共混体系相行为、流变性质、微结构演变及超声增容规律，探讨建立共溶质场中超声增容后蛋白-多糖共混体系相分离/胶凝耦合竞争-微结构-物性的关联关系，并通过数值模拟溶胶-凝胶转变过程，阐明凝胶形成机理，为凝胶食品产品的物性设计和规避产品质量缺陷奠定理论基础。

共溶质场中多元食品高分子共混体系的溶胶-凝胶成型制备理论尚未完善。本项目借鉴材料科学领域聚合物共混理论用于研究食品凝胶产品控制胶凝与控制成形，我们首先研究了蛋白-多糖溶液共混物的相行为，在此基础上选定模拟凝胶糖果、果冻及素食三类食品凝胶产品的蛋白-多糖共混溶液模型体系，围绕共溶质场中蛋白-多糖共混体系超声增容规律及溶胶-凝胶转变动力学、凝胶形成机理进行了系列研究。基于对明胶/变性淀粉共混体系相转变G′-t曲线求一阶及二阶导数，我们发现分别有四个特征温度值存在于溶胶-凝胶转变过程并将其分为五个阶段，随葡萄糖浆浓度增加，相转变过程高温区凝胶活化能值（Ea）呈先降低后增加趋势，低温区Ea则无显著变化，当该共混体系同时添加蔗糖共溶质和进行超声处理时，超声处理产生的降解增容效应占主导，可阻滞凝胶化形成，解析了明胶/变性淀粉共混体系相行为趋势、溶胶-凝胶转变动力学及凝胶机理；低浓度蔗糖共溶质场中通过增加琼脂/魔芋胶共混体系中琼脂分子间的氢键作用，可促进琼脂分子形成双螺旋结构，显著降低高温区的凝胶Ea，进而交联形成细密、平整的网络结构，改善了共混体系凝胶的流变及质构凝胶特性，在揭示该共混体系相行为演变趋势原因基础上阐明了琼脂/魔芋胶共混体系的溶胶-凝胶转变机理；未经超声处理时，随蔗糖共溶质浓度增加，可显著提升大豆蛋白/魔芋胶共混体系的弹性模量（G′）、凝胶化速度、共混凝胶的硬度及粘附性，但未添加蔗糖条件下超声处理明显弱化了共混体系的此四参数值，伴随微观结构发生团块状聚集化，明确了大豆蛋白/魔芋胶共混体系共溶质-微观结构-物性间的关联关系，并证实了超声可抑制蔗糖共溶质提高该共混体系的凝胶强度。本项目的研究成果有望为食品凝胶产品的工艺优化及质量控制提供应用理论基础指导。