pH对鳜鱼肌原纤维蛋白凝胶特性的影响

Effects of pH on gel properties of mandarin fish(Siniperca chuatsi)myofibrillar protein

该文通过测定鳜鱼肌原纤维蛋白热诱导凝胶的凝胶强度、质构和巯基含量等指标,以及运用SDS-PAGE、低场核磁和拉曼光谱、扫描电镜等技术手段,探究不同pH(9.0~4.0)对鳜鱼肌原纤维蛋白(myofibrillar protein,MP)热诱导凝胶的物性、水分状态、结构特征的影响。结果表明,pH对该蛋白凝胶特性具有显著的影响。随着pH值的降低,鳜鱼MP凝胶强度和质构先升高再降低,在pH 5.0时达到最大值,并且此时的热诱导MP凝胶特性最好;SDS-PAGE结果表明,pH值从5.0降低到4.0时,肌原纤维蛋白和肌动蛋白发生降解,但从凝胶表观图上来看,pH 6.0的MP凝胶表面更光滑均匀;二级结构结果表明,当pH值从7.0降低到4.0时,MP的多肽链受酸性增强作用而阻碍其展开和转化,从而使MP凝胶基质在凝胶形成过程中逐渐变成无序结构;在pH 6.0时,凝胶结构趋于有序,形成多孔且孔径均一的细致结构。疏水相互作用与巯基含量在pH 6.0时达到最大值。综合分析表明,鳜鱼MP热诱导凝胶在pH 6.0时凝胶状态最好。因此,鳜鱼肌原纤维蛋白凝胶具有开发成功能性鱼制品的潜力。

The function of fish protein gel is strongly influenced by pH.Under different pH conditions(9.0-4.0),the physical properties,moisture state,and structure characteristics of heat-induced gelation of myofibrillar proteins(MP)from mandarin fish(Siniperca chuatsi)have been studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE),low-field nuclear magnetic resonance(LF-NMR),Raman spectroscopy,scanning electron microscope(SEM),and other technologies,focusing on indicators such as gel strength,texture,and sulfhydryl group content.Results showed that pH had a significant effect on the properties of the fish protein gel.With the decrease of pH value,the strength and texture of MP gel of mandarin fish firstly increased and then decreased,reached the maximum value at pH 5.0,and the properties of heat-induced MP gel achieved the best at the same time.SDS-PAGE results showed that myofibril protein and actin were degraded when pH was decreased from 5.0 to 4.0,but the surface of MP gel at pH 6.0 was smoother and more uniform from the gel appearance diagram.The secondary structure results showed that the polypeptide chains of MP were hindered from unfolding and transforming by the acidic enhancement when pH was lowered from 7.0 to 4.0,thus the MP gel matrix gradually turned into a disordered structure during the formation of gel.The structure tended to be ordered at pH 6.0,forming a detailed structure with porous and uniform pore size.The hydrophobic interaction and thiol content reached maximum at pH 6.0 as well.In conclusion,the state of heat-induced MP gel achieved the best at pH 6.0.Therefore,the MP gel of mandarin fish has great potential to the development of functional fish products.