Influence Of Protein Oxidation On Myofibrillar Proteins Degradation And Meat Eating Quality From Bovine During Postmortem Ageing

1. Influence of oxidation on myofibrillar proteins degradation from bovine via μ-calpain.The objective of this study was to investigate the effect of oxidation on proteolysis of myofibrillar proteins via μ-calpain. Myofibrillar proteins prepared from bovine muscle were exposed to in vitro oxidation to produce varying levels of protein modification by use of H2O2and Fe2+. Protein oxidation level was measured by the carbonyl content. Modified proteins were then incubated with active μ-calpain, and the rates of protein degradation were analyzed via SDS-PAGE and western blotting. Results revealed that increased protein oxidation enhanced the degradation of myosin heavy chain (MHC) and a-actinin, reduced the degradation of38kDa troponin-T but had little influence on the30kDa degradation fragment derived from troponin-T and the degradation of actin. These findings demonstrated that oxidative modification of myofibrillar proteins changed their susceptibility to μ-calpain and provided a mechanistic link connecting oxidation with myofibrillar proteolysis and, as such with meat tenderness.2. Influence of μ-calpain oxidation on bovine myofibrillar proteins degradation in vitroThe objective of this study was to investigate the influence of oxidation on the bovine myofibrillar proteins degradation.μ.-calpain was oxidized by varying concentrations of oxidant (H2O2and Fe2+), then incubated with purified bovine myofibrillar proteins, and the rates of protein degradation were analyzed via SDS-PAGE and Western blotting. Results revealed that the ability of μ-calpain in degradating desmin and troponin-T was attenuated as the oxidative level increased, meanwhile, the30kDa degradation fragment derived from troponin-T was inhibited. Overall, oxidation of μ-calpain limited its ability in degradating a part of myofibrillar proteins.3. Influence of oxidation on beef attributes during postmortem ageing The objective of this study was to investigate the influence of protein oxidation on bovine edible qualities and myofibrillar proteins degradation during postmortem ageing. Beef was injected immediately with varying concentrations of oxidant (H2O2) after slaughtering, then was packaging by vacuum and displayed for14days at4℃. Edible qualities such as pH, cooking loss, shear force were evaluated, and moyfibrillar proteins degradation was analyzed by SDS-PAGE and western blotting during the storage. Results showed that protein oxidation inhibited the processing of postmortem ageing, especially meat tenderness after7d. SDS-PAGE and western blotting showed the degradations of desmin and troponin-T were inhibited after3d. Moreover, the oxidation increased pH from12h to24h while had no significant influence on cooking loss.