Characterizing myoglobin phosphorylation and its relationship with beef color stability

This seed grant proposal addresses USDA AFRI program area priority Improving Food Quality (Program Area Priority Code - A1361) through understanding the physical, chemical, and biological properties of foods. Customers rely heavily on fresh meat color as an indicator of wholesomeness, and color of fresh beef is a major quality attribute influencing the purchase decisions at the point-of-sale. It has been estimated that the U.S. beef industry incurs an annual revenue loss of $1 billion as a result of discoloration. Myoglobin is the sarcoplasmic heme protein responsible for meat color, and the interinfluential interactions between myoglobin and biomolecules in the sarcoplasm govern color stability in fresh meats. Recent results from our laboratory indicated the possibility that beef myoglobin is phosphorylated and suggested a possible relationship between this post-translational modification and beef color stability. Recently attempts were made to evaluate the relationship between protein phosphorylation and meat quality, and the foci of these investigations were tenderness and the conversion of muscle to meat. Previous investigations in agricultural and medical sciences characterized phosphorylation of several muscle proteins, including human myoglobin. However, no investigations were undertaken to examine this biologically important post-translational modification in myoglobins of food animals. We hypothesize that beef myoglobin undergoes phosphorylation in post-mortem skeletal muscles during wet-aging and that phosphorylation influences myoglobin redox stability and retail color stability of fresh beef. The specific objectives of this seed grant proposal are: (1) to identify the sites of phosphorylation in beef myoglobin; (2) to determine how post-mortem aging influences phosphorylation of beef myoglobin; and (3) to characterize the relationship between myoglobin phosphorylation and beef color stability. Characterizing the biochemistry of phosphorylation in beef myoglobin will enable determining the impact of this post-translational modification on myoglobin redox stability and beef color stability. This will also aid developing novel processing strategies to minimize discoloration in and to improve marketability of whole-muscle beef cuts. In addition, the preliminary data generated from this seed grant will be utilized for submitting a research grant proposal to the USDA AFRI Competitive Grants Program, tentatively entitled - "Phosphorylation of livestock, poultry, and fish myoglobins: Implications in muscle food color stability".