Abstract
The seasonal change in levels of the chemical constituents in the whole body of the Pacific oyster, Crassostrea gigas, cultured by the single seed method in Akkeshi, Hokkaido was investigated. The whole body weight after shelling and the soft tissue index were at the lowest levels in August 2004 and September 2005 after the spawning season. The protein content increased before and after the spawning season. The level of glycogen decreased to less than 10% on a dry matter basis before and after the spawning season, although it increased to more than 20% from autumn to spring. The total content of adenosine triphosphate (ATP) and related compounds was the highest in November and the lowest in September. The levels of total free amino acids were highest in June and lowest in September, the major amino acids being taurine, alanine, proline, glycine, and glutamic acid. A sensory evaluation revealed that the extract prepared from specimens in November was milder in taste and weaker in bitterness than that prepared from specimens in September.
