Effect of blood deposition phenomenon on flesh quality of yellowtail (Seriola quinqueradiata) during storage

Abstract We examined the influence of blood deposition on flesh quality of ordinary muscle in yellowtail. This study compared the flesh quality changes in upper and under‐sides of yellowtails killed by two different methods: spinal‐cord destruction (SCD) with blood removal and suffocation in air without blood removal (SA). The under‐sides of the SA group showed the highest values for a *, cathepsin B and B + L activities, the lowest value in breaking strength and the greatest degradation of myosin heavy chain (MHC) among the four groups. However, the values of the SCD‐upper group indicated the best flesh quality. In addition, the white blood cells presented the highest cathepsin B and B + L activities among the blood components. These results indicate that blood has the tendency to deposit downward in accordance with the direction of placement. This phenomenon influences the distribution of white blood cells which contain enzymes that accelerate the deterioration of flesh quality. The texture of fish muscle is an important part of the flesh quality. In captured fishery (purse‐seine fishery and dragnet fishery), it is impossible to immediately and completely remove blood. Therefore, suffocation in air is the common method after the fish is caught. The commercial value of fish is decreased and the price varies greatly when these fish enter market circulation. In our study, we examined the influence of blood deposition on the flesh quality of yellowtail during storage. The degradation of structural proteins accelerated in the deposited blood which contain proteases. The movement and deposition of blood caused the difference of quality on both sides, which seriously affected the quality of fish during preservation. Our study has some theoretical guidance for muscle softening and give a better understanding of the adverse effect of blood during preservation.