丙二醛氧化对牦牛肉肌原纤维蛋白结构及功能特性的影响

Effect of Malondialdehyde Oxidation on the Structure and Functional Properties of Myofibrillar Protein in Yak Meat

利用丙二醛建立脂质氧化体系,通过测定牦牛肉肌原纤维蛋白(myofibrillar protein,MP)的侧链氨基酸氧化情况、蛋白结构、流变特性、乳化稳定性等变化,探讨不同程度的脂质氧化对牦牛肉MP结构与功能特性的影响。结果表明:随着丙二醛浓度(0、0.1、1、5、10、20 mmol/L)增加,MP的羰基含量、丙二醛-MP加合物、二聚酪氨酸含量以及β-转角相对含量整体呈增加趋势;总巯基含量、表面疏水性、内源荧光强度、α-螺旋和β-折叠相对含量整体呈下降趋势;十二烷基硫酸钠-聚丙烯酰胺凝胶电泳结果表示肌球蛋白重链和轻链逐渐损失。说明丙二醛与MP发生相互作用引起MP氧化、交联聚集并使蛋白结构从有序转为无序。此外,适度氧化(<10 mmol/L)能提高MP储能模量和损耗模量,改善MP的凝胶质量。但过度氧化(≥10 mmol/L)会引起蛋白质高度聚集,导致储能模量和损耗模量降低,且丙二醛氧化会导致MP乳液稳定性降低和色泽的劣变。本研究认为丙二醛氧化促进了牦牛肉MP的氧化,改变了牦牛肉MP的结构与功能特性。

To explore the effect of different levels of lipid oxidation on the structural and functional properties of myofibrillar protein(MP)in yak meat,the oxidation of side-chain amino acids,structure,rheological characteristics,and emulsion stability of MP incubated in the presence of different concentrations(0,0.1,1,5,10 and 20 mmol/L)of malondialdehyde(MDA)were measured.The results showed that with an increase in MDA concentration,the contents of carbonyl group,MDA-MP adducts and dimeric tyrosine and the relative content ofβ-turn in MP overall increased,while total sulfhydryl content,surface hydrophobicity,endogenous fluorescence intensity,and the relative contents ofα-helix andβ-sheet decreased.Sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE)results indicated gradual loss of myosin heavy and light chains,implying that interaction with MDA could induce MP oxidation and cross-linked aggregation and result in structural transition from an ordered to a disordered state.In addition,moderate oxidation(with MAD concentration<10 mmol/L)increased the storage and loss moduli and improved the gel quality of MP;however,excessive oxidation(with MAD concentration≥10 mmol/L)led to serious aggregation of MP and a decrease in the storage and loss moduli as well as a decrease in the emulsion stability and color deterioration.In conclusion,MDA oxidation can promote the oxidation of MP,and alter the structural and functional properties.