Seasonal Variation in the Proximate Composition, pH and Glycogen Content of Oysters Crassostrea gigas Collected in Geoje and Jaran Bay in Korea

The seasonal variation in the proximate composition, pH, and glycogen contents of oysters Crassostrea gigas collected in Geoje and Jaran Bays on the southern coast of Korea was studied between March 2012 and February 2013. In the Geoje Bay oysters, the moisture content was 77.49-81.50 g/100 g, lipids ranged between 1.22 and 2.47 g/100 g, proteins between 9.46 and 13.11 g/100 g, and ash between 1.88 and 2.58 g/100 g. In the Jaran Bay oysters, the moisture content was 74.22-82.05 g/100 g, lipids comprised 1.32-2.37 g/100 g, proteins 9.19-13.35 g/100 g, and ash 1.96-2.45 g/100 g. The moisture content was highest in October and January in Geoje and Jaran Bay, respectively, and tended to increase from July until September. The highest protein levels occurred in August in both bays, which coincided with the timing of oocyte maturation, and then decreased at the beginning of total spawning. The highest lipid levels occurred in April in Geoje Bay, and February in Jaran Bay. The glycogen content was 0.40-2.28 g/100 g in Geoje Bay, and 0.61-3.53 g/100 g in Jaran Bay, and was highest in February and decreased from March onwards. The lowest glycogen content occurred in September and then increased from October onwards. The pH ranged between 6.29 and 6.48, and 6.32 and 6.59, for Geoje and Jaran Bay, respectively, and was highest in February.