Xiaoqing He¹, Wenhong Cao^{1, 2,}, Zike Zhao¹, Chaohua Zhang^{1, 2}

Three types of proteins including sarcoplasmic protein, myofibrillar protein and stromal protein were isolated and from Paphia undulate muscle tissue. Myofibrillar protein had the highest content (45.42%), followed by sarcoplasmic protein (31.20%) and stromal protein (20.69%). Analysis of DSC found that the denaturation temperatures of sarcoplasmic protein, myofibrillar protein and stromal protein were 53.4C, 47.23C and 55.73C, respectively. The three protein fractions contained higher contents essential amino acids, alkaline, hydrophobic and branched chain amino acid. Protein hydrolysates prepared with trypsin revealed a good radical scavenging activity. Moreover, the hydrolysates of sarcoplasmic protein exhibited the strongest radical scavenging activities including DPPH radical, hydroxyl radical and superoxide anion radical, with the IC₅₀ values being 4.82, 4.70 and 3.75 mg/mL, respectively. In addition, the hydrolysates of sarcoplasmic protein and myofibrillar protein showed a similar reducing power and their reducing power were 0.58 and 0.57 at 10 mg/mL, respectively. While the hydrolysates of stromal protein displayed lower reducing power.

protein isolation, DSC, protein hydrolysate, free radical scavenging activity, reducing power