Study on Annual Component Analysis of Pacific Oysters (Crassostrea gigas) and Mussels (Mytilus galloprovincialis)

To study the change in components of Pacific oysters (Crassostrea gigas) and mussels (Mytilus galloprovincialis) over a year, their annual obesity ratio, umami components (glutamic acid and glycogen), functional components (Zn, Mn, Cu, and vitamin B12), and Cd and noroviruses (NoVs) contents were quantified.

In oysters, the obesity ratio, and chemical components showed seasonal changes depending on the spawning season. Glutamic acid content increased from November to March. In contrast, glycogen content peaked in May and November. Mineral content markedly increased during spawning. From the comparison of NoVs GI and GII strains, oyster predominately infected by the GI. A remarkable difference in NoVs contents was observed depending on the oyster farms.

In mussels, glutamic acid, Zn and Cu contents were stable throughout the year. Mussels Cd content was one-fifths that in oysters. Although the NoVs strain was affected by the collection area, mussels from both areas showed decreased NoVs contents in summer, corresponding with the consumption season of mussels in Japan.

Our comparative study on the seasonal variability in the chemical components and NoVs contents in pacific oysters (C. gigas) and mussels (M. galloprovincialis) clearly showed an association of physiological with reproduction and environmental factors on farms.