IOS和MOS对牦牛肌原纤维蛋白生化与功能特性的影响

氧化是调控肉类品质的一种潜在工具,肉类蛋白氧化调控理论的完善有助于其在食品工程中的应用。为了研究不同氧化体系下,牦牛肌原纤维蛋白化学修饰与功能性质之间关系,该研究分析了离子氧化体系(Iron Oxidizing System,IOS)和高铁肌红蛋白(Metmyoglobin Oxidizing System,MOS)氧化体系下在特定氧化程度(蛋白羰基含量)下牦牛肌原纤维蛋白的生化特性、二级结构和功能特性。结果发现,随着氧化强度的提升,牦牛肌原纤维蛋白会发生显著的巯基丧失、二硫键生成、二酪酸增加以及表面疏水性下降现象(P<0.05)。当羰基浓度达到(1.51±0.13) nmol/mg以后,MOS体系的二硫键和表面疏水性变化比IOS系统更明显。此外,随着氧化程度的增加,α-螺旋结构比例会持续减少,而β-折叠与β-转角结够会持续增加。通过对蛋白质功能性功能性研究,还发现适当的氧化对牦牛肌原纤维蛋白的溶解性和乳化性有一定改善作用,其改善峰值和范围因氧化体系不同而有所差异,MOS的功能特性影响对氧化强度更敏感。通过相关性分析可以发现,二硫键与溶解度、浊度、乳化性等功能特性相关性显著,二级结构大多数指标则与溶解性和浊度相关性显著。综上所述,不同氧化体系对于肌原纤维蛋白的生化及功能特性的影响存在差异,MOS系统能够在较小的氧化程度下对功能特性产生改善作用,这与其同时带来的二硫键和表面疏水性更显著的变化有关。

Effects of MOS and IOS on the biochemical and functional traits of myofibrillar proteins of yak

Oxidation is a potential tool to control meat quality,and the improvement of meat protein oxidation regulation theory is helpful to its application in food engineering.The protein oxidation systems in muscle are Ion Oxidizing System(IOS)and Metmyoglobin Oxidizing System(MOS).According to previous study,different oxidizing systems will lead to different oxidation phenomenon.So Elucidating the effects of different oxidation systems on biochemical and functional traits of myofibrillar proteins is helpful to improve the engineering theory and application of oxidation regulation of meat quality,which is more important for yak meat quality control because of its higher iron ion and metmyoglobin content.In order to investigate relationship between functional traits and chemical modification of myofibrillar proteins of yak under different oxidizing systems,the biochemistry traits(sulfhydryl content,disulfide bonds content,bityrosine content and surface hydrophobicity),secondary structure(α-helix percent,β-sheet percent,β-turn percent and random coil percent)and functional traits(solubility,turbidity,emulsifying activity index,emulsifying stability index,foamability and foam stability)of myofibrillar proteins of yak were analyzed under IOS and MOS with similar oxidation degree(protein carbonyl content),meanwhile the correlation coefficient between functional traits and biochemical traits of myofibrillar proteins of yak were also analyzed.It was found that there were significantly decreasing thiol group,increasing disulfide bond,increasing bityrosine and decreasing surface hydrophobicity(P<0.05)with increasing carbonyl concentration.Under IOS surface hydrophobicity insignificantly decrease when carbonyl concentration reached(1.19±0.06)nmol/mg.While the change of disulfide bond and surface hydrophobicity of MOS is more obviously than IOS when carbonyl concentration reached(1.51±0.13)nmol/mg which indicate that MOS is more sensitive to form disulfide bond.According to general liner model analysis,the interaction between oxidizing system and oxidizing degree on disulfide bonds content and surface hydrophobicity is significant which declare that the effects of oxidizing intensity on these chemical traits will be different because of different oxidizing system.When the carbonyl content increases by 1.22 nmol/mg to reach a high level,theα-helix structure will decrease by about 17%,while the proportion of theβ-sheet structure significantly increases by about 13.5%(P<0.05).With the increase of the degree of oxidation,the protein solubility first increased and then decreased.The peak of the solubility appeared at the medium level(carbonyl content(1.51±0.13)nmol/mg).When the oxidation level reached the medium level,the solubility of the MOS system was significantly higher than that of the IOS system,indicating that the solubility change of the MOS system was more sensitive to the oxidation intensity.Moderate oxidation can improve the solubility and emulsification of myofibrillar proteins of yak and the optimal range of improvement depend on oxidizing system.The effect of MOS on functional traits is more sensitive to oxidation degree.Through correlation analysis,it can be found that disulfide bond is significantly correlated with solubility,turbidity,emulsification and other functional characteristics,while the most indexes secondary structure is significantly correlated with solubility and turbidity.It is shown that different oxidation systems have different effects on the biochemical and functional properties of myofibrillar,and MOS system can improve the functional properties at a lower degree of oxidation,which is related to the more significant changes in disulfide bonds and surface hydrophobicity。