## 4 Discussion  
The aim of this study is to carry out a measurement of the E\({}_{\text{h}}\) on a carcass, at the separation between forequarter and hindquarter in order to evaluate, by the measurement of the color transfer a*, the time necessary for meat color to change from red to brown. Since meat is a complex media, linked to the fact no commercial redox probes exist for semi-solid media, a preliminary study was the use of meat juice as a meat mimetic medium. For that, the volume which has been retained is 50 mL so that the redox probes used can be completely immersed. Regarding the dilution, it was decided to modify the juice as little as possible to stay as close as possible to the pure juice, the 1/5 dilution in milliQ water was therefore selected. The more the juice is diluted the more the amount of myoglobin (Mb) present decreases, which can influence the results. In fact, the muscles containing high concentrations of Mb appear darker than those containing less. These differences in myoglobin concentrations, oxygen consumption rate and autoxidation rate may explain the variations in color stability between different muscles [12]. The juice preparation steps are just as important and should be monitored to ensure that they have the least impact on color changes. Pure juice is not a good choice to follow color changes because it is too dark. A 1/5 dilution was applied with two different waters. The results showed that the color change was slowed down with the use of physiological water. Indeed, the use of NaCl is well known to act as a preservative and this can explain this slowing down although the study done by [PERSON] and [PERSON] [13] has highlighted the pro-oxidant effect of NaCl on lipid oxidation and so, on color transfers. In contrast, milliQ water has the same behavior as distilled water and according to the experience of [PERSON] et al. [14] on the preparation of meat juices, distilled water was used and the components in the meat juices were not changed after dilution. This thus validates the method used in this study. Experience on the packaging conditions of meat before freezing has highlighted the fact that the juice extracted from meat frozen in air has a value of a* higher than that of meat frozen in vacuum. This can be explained by the fact that the meat packaged in air was able to oxygenate during the freezing and thawing stages, resulting thus in a higher beginning value. However, no difference was observed on the color transfer itself. According to [PERSON] et al. [15], when fresh meat is packaged with films having a high impermeability to oxygen (under vacuum), anaerobic growth of native microorganisms is favored and the growth of aerobic native microorganisms is limited unlike packaging under oxygen (under air). Moreover, [PERSON] et al. [16] also showed similar results with these two types of packaging. The different types of packaging can influence the color change due to the presence of microorganisms. However the filtration step done in this study has removed all the microorganisms from the juices. This could explain why no difference was observed in the color transfer between the two studied packaging conditions. The centrifugation step did not affect the color transfer but only the initial a* value. Indeed, the non-centrifuged juice has a value of a* higher than the centrifuged juice. This can be explained by the fact that the centrifuged juice has been clarified and is therefore clearer than the non-centrifuged juice. As a result, only the value of a* was impacted. The purpose of the centrifugation step is thus to standardize the juice samples by removing any debris recovered from the juice after thawing and to facilitate filtration. During the experiments on the unfiltered beef juices at 4 \({}^{\circ}\)C and on beef meat at 4 \({}^{\circ}\)C, it was observed that the redox potential and color changes are linked; it is thus possible to follow the color changes using the redox potential and vice versa.