Study On The Effect Of Extracts Of Gnaphalium Affine On The Oxidation,structure And Gel Properties Of Pork Myofibrillar Proteins

Myofibrillar Proteins（MPs）are the main proteins of muscle that determine the quality of meat products.In the process of meat products,oxygen in the air and iron,copper and other metal ions in metal instruments accelerate the catalytic oxidation of muscle proteins.Excessive oxidation of MPs will seriously affect the taste,color,smell,texture and other qualities of meat products.With the improvement of people’s living standard and health consciousness enhancement,green natural food is increasingly favored by consumers,the meat processing industry commonly used traditional synthetic antioxidant face chemical toxicity concerns,have don’t conform to the consumer demand,so the natural antioxidant to replace synthetic antioxidants used in food processing is the trend of the times.Plant polyphenols is research in recent years is the most effective natural antioxidant,mainly because of natural extracts of polyphenols and MPs interaction affect protein amino acid side chains,after the change of protein structure,thus mediated regulation of protein oxidation degree and the protein gel properties,as a breakthrough,a large number of natural antioxidants can be developed to improve the taste,flavor and quality of meat products in actual meat processing.The extract of gnaphalium affine contains rich polyphenols and flavonoids,with antibacterial,anti-inflammatory and antioxidant physiological effects.Existing studies have shown that the extract has strong ability to scavenge free radicals,and can effectively inhibit fat oxidation rancidity,with certain antioxidant potential.Further studies are needed to determine whether the gnaphalium affine extract can mediate the regulation of protein oxidation,structure and functional characteristics.Therefore,this study first used tea polyphenols（TP）and gnaphalium affine extract（GAE）as additives to explore the changes in the oxidation degree,structure and gel properties of MPs.Secondly,the synergistic regulation of GAE and sodium pyrophosphate（PP）on the physicochemical and gel properties of MPs was studied.The main research contents and results were as follows:（1）GAE was obtained by ultrasonic-assisted alcohol extraction and its main components and antioxidant activities were determined in vitro.The results showed that GAE was rich in total flavonoids and total phenols（37.09%and 67.50%,respectively）.GAE had strong free radical scavenging ability,especially the semi-inhibitory concentration of·OH was as high as 3.59μg/m L,which was slightly lower than the standard antioxidant Vc.（2）Taking MPs as the research object,·OH produced by Fenton oxidation system was used to induce the oxidation of MPs,and a series of H₂O₂ concentration gradients（0,1,3,5,10,and 20 mmol/L）were set to explore the oxidation degree of MPs.The results showed that the higher the concentration of H₂O₂,the greater the carbonyl content and surface hydrophobicity,and the lower the total sulfhydryl content and free amino content,indicating that the deeper the oxidation degree,the greater the change of protein amino acid side chain.The concentration of H₂O₂ for moderate oxidation was determined to be3 mmol/L.（3）Adding different concentrations of TP/GAE（0,1.2,6.0,30 mg/g proteins）to regulate moderate oxidation of MPs,and studying the effects of TP/GAE on protein structure,surface properties and solubility.GAE and TP significantly inhibited carbonyl formation and promoted sulfhydryl loss（P<0.05）,especially at high concentrations,TP and GAE inhibited carbonyl formation by 36.89%and 38.93%,and promoted sulfhydryl loss by 28.89%and 27.40%,respectively.Both TP and GAE had a strong quenching effect on the endogenous fluorescence of MPs,which promoted the further expansion of the protein structure,intensified the loss ofα-helical conformation caused by oxidation,exposed more active groups,promoted the formation of a small amount of polymer,and significantly increased the hydrophobicity and insolubility of the protein surface（P<0.05）.The higher the concentration of TP and GAE,the greater the effect on the oxidation and structural changes of MPs,but GAE is less regulated by the oxidation of MPs and the interaction with protein than TP.（4）Adding different concentrations of TP/GAE（0,0.04,0.2,1.0 mg/g proteins）to regulate the moderate oxidation of MPs,and studying the effect of TP/GAE on the performance of protein gel.The results showed that GAE supplemented with 0.2 mg/g proteins could significantly improve the viscoelasticity,gel strength and gel retention of MPs（P<0.05）,and obtain a smooth and compact gel network structure.The addition of TP/GAE with 1.0 mg/g proteins was not conducive to the formation of MPs gel network structure,and the stability of the gel structure was damaged.（5）Under the condition of moderate oxidation of MPs,the degree of oxidation of MPs was regulated by combining GAE and PP,and its effects on protein structure and gel properties were studied.The results showed that GAE and PP had synergistic antioxidant effects by further decreasing carbonyl content,increasing hydrogen bond content and inhibiting the conversion of sulfhydryl group to disulfide bond.An appropriate amount of PP can effectively modify the damage of GAE to MPs structure,maintaining protein structural stability and strengthening the protein gel system.However,excessive PP led to the collapse of the protein gel network,resulting in poor gel quality.