微纳米淀粉增强鱼肌原纤维蛋白凝胶的临界尺度效应及其机制研究

The interaction between starch and protein is employed to reinforce the strength of surimi gel, and it is generally believed that starch had a filling effect. However, we found that starch also showed interpenetrating behavior and interface adsorption. Moreover, micro- and nano-starch (M/NS) had a critical size for the reinforcement of texture of myofibrillar protein (MP) from freshwater fish, but the mechanism is not clear. Based on the critical size, the surface effect, aggregation and molecular structure of are investigated by laser particle size analyzer, XPS, SAXS, solid NMR and SEC-MALLS-VIS-RI. Effect of MS and NS on chemical interactions, molecular conformation, dynamic sol-gel transition and gel network strength of MP is also explored by FTIR-ATR and rheological methods combined with Cross, Burger models and Winter-Chambon criterion. The network density is observed by SEM, and the morphology and spatial partition of MS and NS are detected by light microscopy with eosin/iodine staining. The intrinsic correlation is established among surface effect, aggregation and molecular structure of MS and NS with gel characteristics of MP. Consequently, the relative contributions of surface effect, aggregation and molecular structure of MS and NS to gelation properties and network structure of MP are determined by correlationship analysis. This work will reveal the mechanism of critical size effect of M/NS for the reinforcement of MP gel network, amend the processing theory of surimi products and provide a reference to study the macromolecular interaction between polysaccharide and protein under gel state.

利用淀粉-蛋白互作改善鱼糜制品凝胶强度，普遍认为淀粉是填充效应。然而前期发现两者还存在互穿和界面吸附，且当淀粉颗粒处在特定微、纳米尺度和比例(临界尺度)时可显著增强鱼肌原纤维蛋白(MP)凝胶，其机制是否与互穿、界面吸附以及淀粉表面和结构有关尚不明确。本项目拟针对该尺度淀粉的微米(MS)和纳米级分(NS)，运用XPS、SAXS、固体NMR和LLS研究表面效应、聚集态和分子链结构；采用FTIR-ATR、DSC、流变学方法结合Winter-Chambon、Burger模型，分析MS和NS对MP化学键力、分子构象、溶液-凝胶转变及凝胶强度的影响，研究MS和NS在网络中互穿行为和界面吸附，明确MS和NS增强蛋白胶凝的焓或熵驱动；比较MS和NS、淀粉表面和结构对MP胶凝特性及网络结构的贡献，阐释MNS增强MP凝胶的临界尺度效应机制。研究可完善鱼糜加工理论，也为凝胶态下多糖与蛋白互作机制的探究提供借鉴。

为了改善淡水鱼鱼糜制品的凝胶品质，通常会外源添加淀粉。本实验室前期研究发现纳米尺度淀粉对鱼糜凝胶的增强效果不同于微米尺度的淀粉，纳米淀粉除通过填充效应来增加鱼糜凝胶外，是否还存在界面或网络互穿效应尚不清楚。因此本项目旨在探究微米级、纳米级淀粉与肌原纤维蛋白（MP，鱼糜凝胶制品中的主导蛋白）的相互作用，阐释其影响MP胶凝特性的内在机制。本项目通过高能湿法球磨制备了微米级（MS）和纳米级（NS）的淀粉，首先研究了MS与NS的聚集态结构、分子链结构、表面特性及其物化特性。发现球磨淀粉颗粒尺寸一旦进入到纳米级，展现出显著增强的表面效应（比表面积大和表面活性基团多），且NS结晶结构完全消失以无定形态存在，产生了大量游离的线性直链和支链片段，从而表现出优异的分散稳定性和冷水可溶性。其次，将MS和NS添加到蛋白中进一步探究了MS及NS对MP溶胶及凝胶性质的影响。稳态剪切试验结果显示，MS及NS的添加均使MP/淀粉复合溶胶的假塑性降低、稠度增加；动态频率扫描结合蠕变测试结果显示，NS对MP凝胶劣化的抑制作用及对MP凝胶的增强作用均优于MS；在添加破断剂抑制MP二硫键或疏水相互作用的情况下，相较于MS，NS的添加对MP质构及粘弹性的降低具有更显著的抑制效果。此外，NS在增强MP的凝胶强度、持水性方面均明显优于MS，且NS更有利于MP三维网络结构的均一性和连续性。经相关性分析发现，MP/淀粉复合物凝胶特性的增强与淀粉粒径呈显著负相关，与比表面积及表面活性基团含量呈显著正相关；而MP/淀粉复合物三维网络结构的连续性及均一性与粒径呈显著负相关，与淀粉的分散液稳定性及冷水可溶性呈显著正相关。根据上述显著相关因子进一步分析，NS优异的表面特性、冷水溶解性及分散稳定性促进了淀粉表面基团与蛋白基团的相互作用，其中大量游离的直链和支链片段可与蛋白链相互作用形成互穿网络，促进NS与蛋白形成空间相容体系，最终增强了复合体系的凝胶特性。