Twenty-four skipjack groups subjected to various combinations of prefreezing treatment, freezing, storage, and thawing conditions were examined for the amounts of glycolytic intermediates, ATP, and NAD formed in frozen and defrozen meat. The prefreezing treatments adopted were: leaving fish on board for 15 min or 3hr, and immersion in iced sea water for 12hr. Some fish were frozen immediately after instant blowing. The freezing methods used were air-blast freezing at about -50°C, and two kinds of brine immersion freezing at -17 ?? -20°C and -7.5 ?? -14°C. Storage was carried out for one month at -40, -20, -17, and -13°C. Thawing was performed by leaving the fish overnight in still water at 5°C, in running water at 14°C, and in air at 13°C.
Results showed that in all the groups stored at -40°C, glycogen in the meat was decomposed to lactic acid, the level of G6P not increasing significantly. In the groups stored at -17°C, the level of G6P in the meat increased to some extent when thawed.
The NAD content in the meat decreased sharply during storage at either -13°C or -20°C with a temperature rise up to -2°C. In these cases, a noticeable accumulation of G6P was observed in the defrozen meat. The G6P content was lower in the skipjack which was left standing for 3 hr on board before freezing and then frozen slowly.
