Seasonal Variations of Free Amino Acids in Oyster Whole Body and Adductor Muscle

Abstract

Seasonal variations in the level of free amino acids (FAA) and nonprotein nitrogen (NPN) were investigated in the whole body and adductor muscle of cultured oyster Crassostrea gigas. In the whole body, glutamic acid, alanine, glycine, proline, and β-alanine were abundant. There were marked seasonal variations in level of almost all FAA with a maximum in November to March and with a minimum around August, suggesting that the oyster meat is more palatable in winter to early spring than in summer. Taurine was also abundant in the whole body but showed maximum and minimum levels in June and September, respectively. In the adductor muscle, arginine was found to be rich in addition to the FAA present in the whole body. The FAA levels exhibited pronounced seasonal fluctuations with a maximum in November to April and with a minimum in either July or August. Taurine showed a trend similar to that of the whole body. NPN levels in both whole body and adductor muscle peaked in March and came to the bottom in July. © 1989, The Japanese Society of Fisheries Science. All rights reserved.