Effect Of Pyrophosphate-induced Structural Changes Of Oil-water Interface Proteins On Oxidative Stability And Emulsifying Properties Of Emulsion

The quality of ground meat products is closely related to the structure of the fat interface protein in the emulsification system.Muscle proteins are susceptible to oxidation during processing and storage,leading to huge changes in their structure.Phosphate as a commonly used additive in meat products can change the structure of muscle protein and also change the protein oxidation mode.The impact of these changes on the emulsification performance of muscle protein is not clear.In this project,the myofibrillar protein of pork spine was taken as the research object,followed by pyrophosphate（TSPP）treatment,myofibrillar protein-soybean oil emulsification system establishment,and hydroxyl radical model（FeCl₃/ascorbic acid/H₂O₂）oxidation To observe the effect of TSPP on the oxidative stability,emulsification performance and interfacial adsorption protein structure of the emulsion.The main research contents include:（1）Study the effect of TSPP treatment on emulsion oxidation stability;（2）Study the effect of TSPP treatment on emulsion emulsification performance;（3）Study the effect of TSPP treatment on interface protein structure during emulsification adsorption and oxidation,And analyze the correlation between oxidative stability,emulsification performance,and interface protein structure.（1）Study the effect of TSPP on the oxidation stability of the emulsion.It is found that for the emulsion without TSPP treatment（–TSPP）,as the H₂O₂ concentration increases,the carbonyl content and surface hydrophobicity gradually increase,and the thiol and endogenous tryptophan fluorescence The intensity gradually decreases.TSPP treatment（+TSPP）significantly inhibited the increase of carbonyl and surface hydrophobicity（P?0.05）,as well as the loss of sulfhydryl and endogenous tryptophan（P?0.05）,and as the TSPP concentration increased,this inhibitory effect was more Strong.When heavily oxidized,the carbonyl content of the emulsions in each group increased by 86.80%（–TSPP）,59.73%（1mmol/LTSPP）and 48.49%（5 mmol/LTSPP）compared to the unoxidized;the hydroxyl loss rates were 13.8%（–TSPP）,10.24%（1 mmol/LTSPP）and 9.3%（5 mmol/LTSPP）.It shows that TSPP can protect myofibrillar protein from free radical attack to a certain extent.Myofibrillar protein adsorbed on the lipid surface is the preferred target of free radicals,which can inhibit lipid oxidation,and TSPP treatment can enhance the inhibition of myofibrillar protein on lipid oxidation.（2）To study the effect of TSPP-treated protein on the emulsion emulsification performance,it was found that no matter whether the protein in the emulsion was treated with TSPP or not,as the concentration of H₂O₂ increased,the emulsion stability,gel strength and water holding capacity of the emulsion decreased,and the emulsion liquid The droplets aggregated,the average particle size increased,and the amount of interfacial protein adsorption increased.When the oxidation conditions are the same,the 1 mmol/L and 5mmol/L TSPP treatments have a certain stabilizing effect on the emulsion,which is reflected in the increased emulsification stability,enhanced shear dilution resistance,smaller oil droplet size and more dispersion.Moreover,TSPP treatment significantly improves the strength and water retention of the emulsion gel（P?0.05）.（3）The effect of TSPP treatment on the interface protein structure during emulsification adsorption and oxidation was found.For samples without TSPP and oxidation treatment,the changes in hydrogen bonding,hydrophobic force,and disulfide bonding caused by emulsification adsorption were 33.86%,29.02%and 13.74%,it can be seen that the hydrogen bond and the hydrophobic force are the main chemical forces of myofibrillar protein adsorption at the oil droplet interface.During TSPP treatment,the changes of the three are reduced,especially when 5 mmol/LTSPP treatment,the changes of hydrophobic force and disulfide bond are reduced to 1.23%and 8.65%,respectively.When the emulsion was oxidized,the hydrogen bond content between the interface proteins in the–TSPP and+TSPP samples decreased,and the hydrophobic interaction force and disulfide bond content both increased.During emulsification,adsorption and oxidation,the interface protein will be de-helixed.The reduction ofɑ-helix is related to the degree of oxidation and the amount of TSPP added:heavy oxidation（20 mmol/L H₂O₂）>light oxidation（1 mmol/L H2O2）>Unoxidized,–TSPP>1 mmol/L TSPP>5 mmol/L TSPP.Analysis of the correlation between the interface protein structure and the oxidative stability and emulsification performance of the emulsion under TSPP conditions revealed that the exposure of hydrophobic groups on the surface of the TSPP will make the stability of the gel network structure worse（P<0.05）,hydrogen bonding plays a role in maintaining the emulsion emulsification performance;As the degree of oxidation deepens,the content ofα-helix and hydrogen bonds decrease,and the gel strength is significantly positively correlated with the content ofα-helix（P<0.05）.After TSPP treatment,the correlation between hydrogen bond and emulsification performance was weakened;when TSPP was 5 mmol/L,disulfide bond,hydrophobic interaction and storage modulus were positively correlated（P>0.05）,indicating that moderate oxidation helps to improve Storage modulus;TSPP weakens the correlation between oxidation and hydrophobic group exposure,thereby stabilizing the gel network structure.It shows that TSPP treatment mainly affects the oxidation stability and emulsification performance by stabilizing the protein structure in emulsion emulsification adsorption.In summary,this topic clarifies the correlation between emulsion oxidation stability,protein emulsification performance and interfacial protein structure under the action of phosphate,reveals the structural factors affecting emulsification performance,in order to provide a certain theory for the improvement of meat product quality basis.