Changes in Contents of Free Amino Acids, Trimethylamine, and Nonprotein Nitrogen of Oyster during Ice Storage

Abstract

The contents of free amino acids (FAA) in the whole body and adductor muscle of oyster Crassostrea gigas, which had been stored in ice until they reached early stage of spoilage, were measured. Trimethylamine (TMA), and nonprotein nitrogen (NP-N) together with volatile base nitrogen (VB-N) and trimethylamine oxide (TMAO), were also determined. The content of VB-N at 0 day was relatively low (10.5 and 8.7 mg/100 g) and increased significantly thereafter in both the whole body and adductor muscle during storage for 2 weeks. Only a little TMAO was detected and TMA was about 5 mg/100 g; there was almost no change in the contents during storage in either the whole body or adductor muscle. NP-N was 485 mg/100 g in the whole body and 515 mg/100 g in the adductor muscle at 0 day, and no measurable change thereafter. In fresh whole body, the level of taurine was extremely high (974 mg/100 mg) and the amounts of glycine, proline, glutamic acid, and alanine were relatively large. Taurine and glycine changed little throughout the storage period. Alanine showed a slight increase, while proline and glutamic acid decreased. In fresh adductor muscle, the level of taurine was also high (768 mg/100 g) and the levels of glycine, β-alanine, arginine, alanine, and proline were relatively high. Taurine and glycine exhibited little change during storage. Remarkable increase in alanine and decrease in glutamic acid levels were observed. © 1986, The Japanese Society of Fisheries Science. All rights reserved.