Abstract
The Pacific oyster, Crassostrea gigas, sexually differentiates each year during the reproductive season. According to those
involved in oyster aquaculture, the taste of mature oysters differs depending on sex; however, these taste comparisons have not been
scientifically reported. In this study, we used a microscope to observe the sex differentiation of oysters caught in four collections
in April and May. Sexes of most oysters could not be distinguished in mid-April; however, sex was discriminated in all oysters in
May, which was the maturation stge before relesing egg and spawning. Extracts of oysters from the period when the sexes were
identified were subjected to chemical component analysis; the levels of free amino acids, ATP-related compounds, and glycogen were
quantified, and each sex underwent sensory evaluation. The results showed that males contained more glycine related to sweetness,
aspartic acid for umami, and arginine for bitterness, which are characteristics of marine products, than females. In addition, the
sensory evaluation in late May revealed “sweetness,” “umami,” “oyster-like smell,” and “preference” to be significantly higher in
males and females, although no difference was observed in the sensory evaluation two weeks ago. Adenine, which is not usually
detected in ATP-related compound analyses, was only detected in males during the reproductive stage.
