Non-enzymatic Oxidation Mediated Oxidation Of Pork Myofibrin

In the process of production,processing,storage and transportation of meat products,protein oxidation will affect the edible value and nutritional value of meat products,which is one of the main factors causing the quality deterioration of meat products.Post-slaughter meat products will continuously release free metal ions due to the destruction of their internal tissue structure（the content of iron ions and copper ions occupy the first two positions）,and their own metabolism can produce reactive oxygen species,such as hydrogen peroxide,which can form a Fenton-type oxidation system to promote the further oxidation of proteins.In the production and processing of meat products,salts such as NaNO₂ or NaCl are often added,which can not only maintain the attractive color of meat products,improves the flavor and texture of meat products,but also inhibit bacteria and prevent corrosion,and prolongs the storage period.Their addition also complicates the chemical composition of processing meat products.This topic uses myofibrillar protein as the research model of meat products,and simulates the tissue environment of post-slaughter meat products by adding exogenous metal ions,to explores how NaNO₂ and NaCl affect the protein oxidation process mediated by Fenton-type oxidation system,and in-depth study of the active substances produced in the process.This topic can provide novel insights into the Fenton system and related research on reactive oxygen species,reactive nitrogen species,and reactive chlorine species in food,environment,biology,chemistry and medicine.Mainly from the following three aspects:（1）In the myofibrillar protein model,we explored how NaNO₂ affects the protein oxidation process mediated by the Fe-Fenton system.By measuring carbonyl,sulfhydryl,tryptophan and dityrosine and other protein oxidation indicators,the study found that with the addition of NaNO₂,the Fe-Fenton system-mediated protein oxidation was intensified.In addition,HPLC-MS experiments showed that the addition of NaNO₂ enhanced the nitrification of protein tyrosine,and produced 3-nitrotyrosine（3-NT）in the process of oxidizing protein and tyrosine,which is not only a proof of the existence of active nitrogen free radical（RNS）,but also one of the biomarkers of protein oxidation.（2）In the myofibrillar protein model,the mechanism of NaNO₂ affecting the Fe-Fenton reaction was explored.It was found by TMB experiment that NaNO₂ significantly improved the oxidation capacity of Fe-Fenton system,and it could be seen that NaNO₂improved the catalytic capacity of Fe³⁺under different pH conditions.By monitoring the formation of Fe²⁺in NaNO₂-Fe-Fenton system,it is found that NaNO₂ accelerates the valence state cycle between Fe³⁺and Fe²⁺,accelerates the rate-limiting step of Fe-Fenton reaction,and significantly enhances the reaction activity of Fe-Fenton reaction.In addition,through TPA fluorescence experiment,EPR experiment and HPLC-MS experiment in（1）,it was found that NaNO₂ can generate RNS by scavenging·OH and affecting the Fenton reaction mechanism.（3）In the myofibrillar protein model,we explored how NaNO₂ affects protein oxidation mediated by Cu-Fenton system and how NaCl affects protein oxidation mediated by Fe-Fenton system.Similar to the NaNO₂-Fe-Fenton system,the study found that NaNO₂significantly improved the ability of the Cu-Fenton system to oxidize TMB,and NaNO₂ could also promote the reduction of Cu²⁺by H₂O₂,accelerate the valence cycle between Cu²⁺-Cu⁺-Cu²⁺,thereby accelerating the rate-limiting step of the Cu-Fenton reaction,significantly improved the reactivity of the Cu-Fenton system,and scavenged the·OH produced by the Cu-Fenton reaction to generate RNS,thereby aggravating protein oxidation and nitration.It is also found that NaCl can improve the oxidation ability of the Fe-Fenton system,and improve the catalytic ability of Fe³⁺,promote the valence cycle between Fe³⁺/Fe²⁺in the Fe-Fenton system,and significantly enhance the reaction activity of Fe-Fenton reaction,reaction with·OH forms reactive chlorine radicals（RCS）,which promote protein oxidation.