Decomposition of Glycogen and Protein in Pickled Oyster during Fermentation with Salt

In order to study the decomposition process of glycogen and protein of oyster during fermentation with salt, and the relationship between their breakdown products, the amounts of free reducing sugars and lactic acid were determined, and amino acid compositions were analysed. In addition, the amount of the available lysine which may help us to estimate the reaction of the free reducing sugars with the free amino acids was also determined. Glycogen and protein were gradually decomposed to free reducing sugars and lactic acid, and free amino acids, respectively, and the available lysine was slightly decreased during the fermentation process. Glutamic acid, aspartic acid, lysine and proline were relatively rich in the amino acid com-position of raw oyster protein while amino acids such as tryptophan, methionine, histidine and tyrosine were poor. It was noted that the decreased amino acids in the protein from the fermented oyster were valine, histine, isoleucine and lysine. As a respect to the free amino acids, proline, taurine, glycine, glutamic acid and alanine were abundant in the raw oyster and reached up to of the total fret amino acids. In the fermented oyster, proline, glutamic acid, glycine, alanine, aspartic acid and lysine were prevalently contained and marke about of the total free amino acids. The contents of free amino acids such as lysine, arginine, aspartic acid, glutamic acid, cysteine, isoleucine and tyrosine increased during fermentation while those of taurine, proline and leucine decreased.