Effect of fasting on physical/chemical properties of ordinary muscles in full-cycle cultured Pacific bluefin tuna Thunnus orientalis during chilled storage

Abstract

Using the full-cycle cultured (FC) Pacific bluefin tuna [body weight 16.3±1.9 kg (pre-fasting group, pre-FG), 14.2±0.9 kg (post-fasting group, post-FG)], changes in the physical/chemical properties of the cephalal parts of dorsal (D) and ventral (V) ordinary muscles (OM) by fasting (6 days) during chilled storage (4°C) were investigated. Condition factors were 26.7 (pre-FG) and 20.3 (post-FG, P < 0.05). Fasting changed the liver color to green. Fasting also decreased the amount of protein and lipid contents of the DOM and VOM of FC tuna. The breaking strength and pH of the DOM and VOM of post-FG tuna were higher (P <0.05) than for pre-FG tuna during storage. In contrast, the glycogen contents of DOM and VOM of post-FG tuna were lower than for pre-FG tuna. The color values (L*, a* and b*) of DOM of post-FG tuna were lower than for pre-FG tuna throughout the storage period. In addition, the metmyoglobin (metMb) content of DOM of post-FG tuna was lower (P <0.05) than that of pre-FG tuna, and the metMb content of VOM of post-FG tuna remained low after fasting. These results indicate that fasting suppresses deterioration (especially meat color) of FC tuna muscles during chilled storage.