Study On The Edible Quality And Changes During Frozen Storage Of The Important Bivalve Mollusks From Beibu Gulf In Guangxi

Oyster, clam and paphia, as resources of bivalve mollusks, were rich in China, with delicious taste, nutrient-rich and high economic value. In this paper, oyster (Crassostrea rivularis), clam (Meretrix meretrix) and paphia (Paphia undulata) were experimental materials. Proximate compositions, amino acids compositons and non-volatile taste compounds of the three kind of bivalve mollusks were analyzed. Quality changes on bivalve mollusks meat during frozen storage was study, too. The results are shown as follow:The proximate compositions of oyster were protein (8.60%), water content (78.33%), lipid (1.67%), ash (1.57%), respectively. The clam meat contained protein (10.67%), water content (78.33%), lipid (2.99%), ash (1.68%), respectively. The paphia meat contained protein (10.19%), water content (82.07%), lipid (2.64%), ash (1.72%). Glutamic acid, with the highest content in amino acids, existed in the muscle of oyster (157 mg/g protein), clam (157 mg/g protein) and paphia (158 mg/g protein). The oyster, having no limiting amino acid, the tryptophan was the limiting amino acid in the clam and paphia.Non-volatile taste compounds in the three kind of bivalve mollusks were analyzed by the methods of taste active values (TAVs) and equivalent umami concentration (EUC). Glycine, alanine and glutamic acid were the major free amino acids in the bivalve mollusks. The glycine and alanine contributed to sweet taste of oyster and paphia. Glutamic acid contributed to the umami taste of the bivalve mollusks. TAVs of all EUC were great than one, which meant they had a strong umami taste. K+ and Na+ had no direct effect on the taste of the three kinds of bivalve mollusks. Glycogen also could contribute to the taste of meat, except for the clam. The TAVs of betaine in meat were all greater than one, which meant that had a direct effect on the taste of oyster, clam and paphia.Quality changes of oyster, clam and paphia meat was evaluated during frozen storage, by analyzing free amino nitrogen, total volatile basic nitrogen, water content, pH and color. Fresh oyster, clam and paphia were storaged at -18℃and -60℃for three months. Water content of their muscles showed an overall downward trend; pH value changes was irregular; amino nitrogen content and volatile basic nitrogen content gradually increased as frozen storage; both muscle tissue and color were affected by ice crystals formed during frozen storage. In summary, Compared to -18℃, fresh meat had a better quality during-60℃frozen storage. Compared to the fresh meat, pre-cooked meats were less affected during frozen storage.