*2.4. Protein Solubility*

The total protein solubility (TPS) and sarcoplasmic protein solubility (SPS) were measured using the procedure of Li et al. [27]. A 1 g sample of each muscle (six replications per muscle and per aging period) was homogenized with 10 mL cold 0.025 M potassium phosphate buffer (pH 7.2), which was then shaken at 4 ◦C for 12 h and centrifuged at 1500 g for 20 min. The total protein concentrations of the supernatants were assessed using the biuret method [26]. The step of SPS detection was that the muscle sample (1 g) was homogenized in ice-cold 20 mL 0.025 M potassium phosphate buffer (pH 7.2) and then carried out using the same shaking, homogenization, and centrifugation procedures mentioned above. Myofibrillar protein solubility (MPS) was calculated by TPS minus SPS. The value was expressed as micrograms of soluble protein per gram of meat.
