Molecular Mechanism Of The Effect Of Myofibrillar Protein Oxidation On The Gel Properties Of Mutton Batters

Protein plays an important role in the physicochemical properties and functions of meat and meat products.The impact of protein oxidation on food quality,nutrition and safety has attracted widespread concern.Protein oxidation is widely existed in the process of food,especially meat products processing and storage Studies of protein oxidation and its mechanism have an important significance to practically produce meat products,which can provide a theoretical basis for quality control of meat.In this study,the hind leg meat of mutton was used as raw material,and the hydroxyl radical oxidation system（FeCl₃/Asc/H₂O₂）was used to oxidize the hind leg meat of mutton in different degrees to investigate the influence of oxidation on the rheological and textural characteristics of meat.The intrinsic mechanism of protein oxidation on the degradation of mutton chyme quality was further explored.Finally the influence of protein oxidation on the molecular and physicochemical properties of myofibrillar protein oxidation was investigated.The main research results are as follows:1.In order to explore the effect of protein oxidation on the rheological and gel properties of mutton batter,the mutton was subjected to different degrees oxidation.The carbonyl and total sulfhydryl contents of oxidized myofibrilla protein,the rheological properties,texture properties,gel strength,water-holding and color changes of mutton batters were determined and analyzed.The results showed that the carbonyl content significantly increased and the total sulfhydryl content significantly decreased with the prolonging of oxidation time.Dynamic rheological measurements showed that the G’of the mutton batter slowly decreased at20～47℃,increasing the rate of decline at 48～54℃,and rapidly rising at55～75℃ during the heating process.G’gradually rose during the cooling process,and the lower the oxidation time,the higher the G’end point.Moreover,as the oxidation time of the protein was prolonged,the hardness,elasticity,cohesiveness,adhesiveness,chewiness and recovery of the mutton batters were reduced,and the gel strength and water-holding capacity were significantly reduced.The values of L*,a*and W also decreased as the protein oxidation time increased.This study showed that protein oxidation will lead to the deterioration of the rheological and gelatinous properties of mutton batters,which adversely affects the processing characteristics of mutton.2.This study aims to investigate the effects of protein oxidation on the quality characteristics of minced mutton oxidized at 1,3 and 5 h in Fenton oxidation system.The results showed that with the extension of oxidation time,the cooking loss,freeze-thaw loss and pH value of the minced mutton significantly increased,while the emulsification performance decreased.Compared with the control group,the peak area of immobilized water(T₂₂)and free water(T₂₃)in the oxidation treatment group gradually decreased.Scanning electron microscope（SEM）showed that the hole number of the minced mutton increased and the surface became uneven with the extension of oxidation time.The solubility of salt-soluble proteins showed a decreasing trend with the extension of the oxidation time.Compared with the control,the secondary structure of the protein in the oxidized samples were destroyed.As the oxidation time increased,theα-helix content of minced mutton protein significantly reduced,while the percentage of random coils significantly increased.These results indicated that minced mutton protein had undergone significant oxidation in the Fenton oxidation system,resulting in the changes of quality and structure.3.In order to investigate the effect of protein oxidation on the physicochemical and molecular properties of mutton myofibril,dimeric tyrosine,surface hydrophobicity,ultraviolet spectrum,endogenous fluorescence,infrared spectrum,particle size,and SDS-PAGE were analyzed.The results showed that the contents of carbonyl,tyrosine dimer and surface hydrophobicity of myofibrillar protein increased,the contents of total sulfhydryl group decreased,and the fluorescence intensity decreased with the extension of oxidation time.Oxidation enhanced the particle size of myofibrillar protein and decreased the absolute value of zeta potential.Infrared spectroscopy analysis showed a change in the secondary structure of the protein,theα-helix increased first and then decreased,there was no obvious change in the random coils,while theβ-sheet showed a decreasing trend,and theβ-turn decreased first and then increased.SDS-PAGE electrophoresis indicated that protein oxidation caused cross-linking between proteins.Cys-Cys showed an increasing trend with prolonged oxidation time,and the content of other amino acids showed a decreasing trend with prolonged oxidation time.