Effect of various salts on inosinic acid-degrading enzyme activity in white and dark muscle of the Pacific saury

The Pacific saury is often preserved using salt, which helps to maintain the main taste component of the fish, inosinic acid (IMP). IMP is degraded by the IMP-degrading enzyme IMPase, the activity of which may be differentially affected by the type of salt used for preservation. Understanding the effects of these salts will help to maintain the desired amount of IMP to preserve the taste of saury. In saury, 40 % of all muscle is dark muscle, thereby; therefore, the effect of various salts on IMPase activity should be investigated in both the white and dark muscle. In this study, the IMPase activity in the white and dark muscle of saury was compared under different processing conditions, and the most suitable salts for processing were determined. There was almost no difference in IMPase activity between the white and dark muscle with respect to variations in pH, temperature, and salt type, indicating that the two muscle types could be processed under the same conditions. In addition, IMPase activity in the dark muscle of saury was promoted by MgCl 2 and MgSO 4 , indicating that salt manufactured using an ion-exchange membrane to remove SO 4 2− and to decrease Mg 2+ is most suitable for use in saury preservation.