Oyster Quality Changes During Different Season And Storage

Oyster (Crassostrea gigas) as one of the most important economic bivalves in China, now is widely cultured along the east coast of Shandong Peninsula. Consumers favor oyster for its nutrient function and desirable taste. Therefore, seasonal assessment of oyster chemical compositions, such as glycogen, lipid composition, free amino acid, and heave mental residue is of utility interesting for oyster industry. The glycogen content of oyster is high in the winter and springtime (about 3 g/100g), while low in autumn (about 2 g/100g). The lipid composition shows low contents of neutral lipids and polyunsaturated fatty acids (PUFA) in autumn. The main fatty acids in oyster are palmitic acid (16:0), oleic acid (18:1), eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6). Eicosapentaenoic acid and docosahexaenoic acid together compose over 30% of the total fatty acids. The main free amino acids of oyster are Taurine, Glutamic acid, Glycine, Alanine, Arginine and Proline. Taurine is the most abundant free amino acid (range fom 500 mg/100g to1100mg/100g). Glycogen, lipids and free amino acids of oyster are high in winter and spring than autumn. Heave mental residue in oyster may cause hazards to consumers. Oyster cultured in those place are contaminated with Arsenic (As) and Cadmium (Cd). The concentration of As and Cd are in the range of 1.58-3.60 mg/kg and 1.44-3.32 mg/kg, respectively.Frozen storage can retard many undesirable changes of seafood. But some oxidative reactions, which adversely affect the product quality, still occur. Lipid oxidation is one of the primary causes of quality deterioration of frozen seafood. Oyster is particularly susceptible to oxidative reactions due to high concentrations of polyunsaturated fatty acids (PUFA). PUFA are highly susceptible to oxidation due to the presence of labile double bonds. To restrain the lipid oxidation during frozen storage, many approaches such as glazing with a thin layer of ice are studied. This process can retard the rate of lipid oxidation of meat. Besides, adding antioxidants or...