Improvement in Quality of Skipjackby Instant Killing and Bleeding Machine

摘要

The quality of skipjacks which were caught by purse seine in the Pacific Ocean was compared among three kinds of killing methods: (1) Mechanically instantly killed and bled, followed by frozen in the brine at -17°C and stored at -40°C. The instant killing and bleeding machine takes 3 seconds per one skipjack, (2) Instantly killed by hand, followed by the same treatment, (3) As usual frozen in the brine at -17°C and stored at - 40 °C. The frozen skipjacks were thawed in the refrigerator at 3 °C ～ 5 °C. The meat color (a, b, L values) of skipjack was measured by color difference meter, and lipid content, drip content, pH values and texture of skipjack meat were also measured immediately after thawing, 6 hours and 12 hours after thawing. The skipjacks, which were treated with instant killing and bleeding machine showed remarkably bright red meat color which was similar to that of tuna meat, followed by the skipjacks instantly killed by hand. The highest (a~2+b~2)~(1/2) value was measured in the skipjack treated with the instant killing and bleeding machine. The skipjacks treated as usual showed still dark red meat color and the value of (a~2+b~2)~(1/2) was lowest. The dark red meat color is due to the phenomenon that hemoglobin in the skipjack meat becomes reduced hemoglobin (dark red color) below pH 6.5. Oxidation of myoglobin (metMb) decreased by bleeding.