| Esox lucius and Coregonus peled are characteristic of pisces in Xinjiang. At present, the main of sales are frozen meat.However in storage and distribution processing, often occurs by protein oxidation caused by muscle protein degradation changes, greatly reducing the edible quality and commercial value, to a large extent restricted the growth and development of pisces in Xinjiang.The scarcoplasmic proteins and myofibrillar proteins of muscle of pisces in Xinjiang(Esox lucius and Coregonus peled) was extracted and oxidized by three different oxidizing systems,including hydroxyl radical-generating system,lipid-oxidizing system and oxidase-oxidizing system in this project.Changes of physicochemical properties(carbonyl, dityrosin, total sulfhydry,surface hydrophobicity,free ammonia and ATPase activity),and the change of function properties of nitrogen solubility index,emulsifying properties and so on of oxidized proteins will be studied.Finally the relationship between physicochemical properties and function properties of protein will be explore.In order to prevent Esox lucius and Coregonus peled muscle protein oxidation to provide data support.1 The establishment of the three different oxidizing systemThe proteins of muscle of Esox lucius and was oxidized by hydroxyl radical-generating system, lipid-oxidizing system and oxidase-oxidizing system in this project. Changes of physicochemical properties of oxidized proteins in Esox lucius will be studied.The results showed that high susceptibility of protein to hydroxyl radical-generating system.In the hydroxyl radical-generating system,after oxidizing for 3 h at1~10mmol/L H2O2,the carbonyl content of myofibrillar protein isolate and sarcoplasmic protein were increased by 26.39% and 28.27%.After oxidizing for 1h and 5h at 5mmol/L H2O2,the carbonyl content of myofibrillar protein isolate and sarcoplasmic protein were increased by 7.75% and 7.08%.Therefore, the subsequent experiment of hydroxyl radical-generating system was studied.2 Effect of protein oxidation on physicochemical properties of muscle of Esox lucius and Coregonus peledIn the system,the carbonyl content, dityrosin and surface hydrophobicity of muscle protein were positively correlated with the H2O2 concentration and oxidation time of the oxidant.After oxidizing for 5h at 1~20mmol/L H2O2 in the Esox lucius,compared with the control group,the carbonyl content of myofibrillar protein isolate and sarcoplasmic protein were increased by34.49% and 30.52%. The dityrosin were increased by 43.07% and 30.88%. The surface hydrophobicity were increased by 38.21% and 43.17%. After oxidizing for 1h and 5h at 10mmol/L H2O2 in the Coregonus peled, the carbonyl content of myofibrillar protein isolate and sarcoplasmic protein were increased by 8.03% and 2.59%.The dityrosin were increased by 7.01% and7.57%.The surface hydrophobicity were increased by 17.48% and 7.22%.The total sulfhydry, free ammonia and Ca2+-ATPase activity of muscle protein werenegatively correlated with the H2O2 concentration and oxidation time.After oxidizing for 5h at1~20mmol/L H2O2 in the Esox lucius,compared with the control group,the total sulfhydry of myofibrillar protein isolate and sarcoplasmic protein were decreased by 67.49% and 58.89%.The free ammonia were decreased by 42.62% and 29.93%. The Ca2+-ATPase activity were decreased by 54.55% and 23.61%.After oxidizing for 1h and 5h at 10mmol/L H2O2 in the Coregonus peled,the total sulfhydry of myofibrillar protein isolate and sarcoplasmic protein were decreased by 36.21% and 42.08%,the free ammonia were decreased by 23.02% and 6.89%,the Ca2+-ATPase activity were decreased by 28.81% and 24.07%.The SDS-PAGE electrophoresis patterns also showed that the structure of protein was damaged by protein oxidation.3 Effect of protein oxidation on function properties of muscle of Esox lucius and Coregonus peledThe nitrogen solubility index,emulsifying properties and emulsion stability of muscle protein were negatively correlated with the H2O2 concentration and oxidation time.The turbidity increased significantly with the increase of H2O2 concentration and oxidation time.After oxidizing for 1h and 5h at 15mmol/L H2O2 in the Esox lucius,the nitrogen solubility index of myofibrillar protein isolate and sarcoplasmic protein were decreased by 39.38% and 31.77%, the emulsifying properties were decreased by 13.07% and 19.13%,the emulsion stability were decreased by19.13% and 21.38%, the turbidity always increased. Under the condition of low concentration of oxidant,myofibril protein isolate foaming ability have been improved,but the foam stability of falling,Muscle foamability of sarcoplasmic protein increasing trend on the whole.After oxidizing for 5h at 1~20mmol/L H2O2 in the Coregonus peled,the nitrogen solubility index of myofibrillar protein isolate and sarcoplasmic protein were decreased by 85.35% and67.41%,the emulsifying properties were decreased by 26.36% and 48.78%.The emulsion stability were decreased by 24.76% and 38.49%.In the low concentration of oxidation environment,foamability of myofibril protein increases.Muscle foamability of sarcoplasmic protein changed little, turbidity increased with the increase of concentration of oxidant on the rise.4 Correlation coefficients(r) between the physicochemical and function properties of Esox lucius and Coregonus peledAfter oxidizing of Esox lucius myofibrillar protein isolate,the carbonyl content, dityrosin and surface hydrophobicity with the nitrogen solubility index,emulsification and emulsion stability are negative correlation,and the turbidity is extremely positive correlation(r=0.94,0.90,0.98). The total sulfhydry, free ammonia and Ca2+-ATPase activity with the nitrogen nitrogen solubility index index, emulsification and emulsion stability were very positive correlation, and turbidity is negative correlation.After oxidizing of Esox lucius sarcoplasmic protein,carbonyl content and surface hydrophobicity with the nitrogen solubility index, emulsification and emulsion stability are negative correlation, and with the turbidity and foaming activity is positive correlation.Thetotal sulfhydry and Ca2+-ATPase activity with the nitrogen solubility index, emulsification and emulsion stability were very positive correlation,and with turbidity and foaming activity are negative correlation;The free ammonia with the nitrogen solubility index, emulsification and emulsion stability foaming stability, were positive correlation,and with the turbidity and foaming activity is negative correlation.The dityrosin with the nitrogen solubility index,emulsification and emulsion stability negatively correlated,and with the turbidity were positively correlated.After oxidizing of Coregonus peled myofibrillar protein isolate, nitrogen solubility index and emulsification and emulsion stability with the total sulfhydry, free ammonia and Ca2+-ATPase activity were positive correlation, and with the carbonyl content, surface hydrophobicity and dityrosin were negative correlation. Turbidity with the carbonyl content surface hydrophobicity and dityrosin were extremely positive correlation, and with the total sulfhydry,free ammonia and Ca2+-ATPase activity was negative correlation..After oxidizing of Coregonus peled sarcoplasmic protein. The carbonyl content and surface hydrophobicity with the nitrogen solubility index,emulsification and emulsion stability were negative correlation, with the turbidity and foaming activity are were positive correlation. The total sulfhydry, free ammonia and Ca2+-ATPase activity with the nitrogen solubility index, emulsification and emulsion stability were very positive correlation. |
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