Ice Temperature Technology Regulates The Color Stability And Protein Phosphorylation Level Of Mutton

The objective of this study was to investigate the effects of controlled freezing point storage on muscle color and protein phosphorylation level. The 20 longissimus dorsi of 10 crossbred sheep were used. Compared with refrigeration, the effects of controlled freezing point on muscle color and protein phosphorylation level during storage time were studied. In order to estimate the color stability of meat stored at different temperature, a Konica Minolta colorimeters CM-600d was used to measure instrumental color and reflectance of samples at different wavelengths. Spectrophotometric method was used to assay activity of metmyoglobin reductase and concentration of NADH, so as to analysis the mechanism which about the effect of controlled freezing point storage on color stability. ELISA (enzyme linked immunosorbent assay) was used to test the activity of protein kinase. The phosphorylation level of sarcoplasmic protein and myofibrillar protein in postmortem ovine muscle at different storage temperature were investigated by combination of SDS-PAGE coupled with Pro-Q Diamond and SYPRO Ruby staining. Quantity One software was applied to analysis the optical density of protein bands on SDS-PAGE images. Our study have investigated the causes about effects of controlled freezing point storage on color stability and protein phosphorylation level and provided theory basis to research the mechanism for storage temperature to control the meat quality. The research also supplied reference frame to companies and consumers to produce and select ovine muscle with high quality. The detailed results are listed as follows:(1)The effects of controlled freezing point storage on meat color stability. Meat color was effected by storage temperature and storage time. As the extension of storage time, the a* values, R630/580 values, chroma values and relative concentration of Oxymyoglobin (Oxy%) in refrigeration group were decreased by different degree. At the 6th day, muscle of refrigeration group begin to discolor significantly (p<0.05), and became to be brown stain. However, the a* values, R630/580 values, chroma values and Oxy% in controlled freezing point group stayed at a higher level during the whole storage time and did not show significant changes since the 2nd day (p<0.05). From the 2nd day to the 10th day, concentration of NADH in controlled freezing point group were significantly higher than refrigeration group always. And the MRA of controlled freezine point group was significantly higher than refrigeration group at 2 d and 10 d. All of those indicated that controlled freezing point storage regulates meat color stability by effecting concentration of NADH and MRA. Controlled freezing point storage do great use to maintain meat to be a vivid-red color which was favored by customer.(2) The aim of this study was to investigate the effect of controlled freezing point on protein phosphorylation level, so as to provide a new theoretical basis for controlling meat quality by controlled freezing point. Enzyme linked immunosorbent assay was applied to detect protein kinase activity. A gel-based phosphoproteomic study was performed to analyze the protein phosphorylation in sarcoplasmic proteins and myofibrillar proteins and protein phosphorylation level was tested by SDS-PAGE electrophoresis and fluorescence staining, and was calculated by measuring the fluorescence intensity. At 12 h, the protein kinase activity of controlled freezing point group significantly increased (p<0.05), and from the 12 h to the 9 d the protein kinase activity of the controlled freezing group was significantly higher than the refrigeration group (p<0.05). Globally, the sarcoplasmic proteins of refrigeration group had the higher total phosphorylation level than controlled freezing point group during 12 h to 3 d. However, at 9 d, the total phosphorylation level of the sarcoplasmic proteins of controlled freezing point was higher than refrigeration group. From 24 h to the end of storage, total phosphorylation level of myofibrillar protein of refrigeration was always higher than that of controlled freezing point. The controlled freezing point storage regulated the phosphorylation level of protein by affecting the activity of protein kinase, which can indirectly regulate the meat quality by influencing the glycometabolism, muscle contraction and degradation of skeleton protein.This study suggests that, controlled freezing point storage matained meat color stability effectively by influencing MRA and NADH concentration and regulated protein phosphorylation by influencing the protein kinase activity. And thus controlled freezing point storage controlled the quality of meat.