No abstract

A non-sulfated polysaccharide was isolated from the ink sac of squid Ommastrephes bartrami after removal of the melanin granules. The carbohydrate sequence of this polysaccharide was assigned by negative-ion electrospray tandem mass spectrometry with collision-induced dissociation of the oligosaccharide fractions produced by partial acid hydrolysis of the polysaccharide. The structural determination was completed by NMR for assignment of anomeric configuration and confirmation of linkage information and it was unambiguously identified as a glycosaminoglycan-like polysaccharide containing a glucuronic acid-fucose (GlcA-Fuc) disaccharide repeat in the main chain and a N-acetylgalactosamine (GalNAc) branch at Fuc position 3: -[3GlcAbeta1-4(GalNAcalpha1-3)Fucalpha1](n)-. Partial hydrolysis of the polysaccharide to obtain several oligosaccharide fractions with different numbers of the repeating unit assisted the assignment. In the negative-ion tandem mass spectrometric analysis, the unique (0,2)A type fragmentation was important to establish the presence of a 4-linked fucose in the main polysaccharide chain and a GalNAc branch at the Fuc position-3 of the disaccharide repeat.

A simple method was developed for the determination of biogenic amines in aquatic food products using a reverse-phase high-performance liquid chromatography with postcolumn automatic o-phthalaldehyde derivatization and fluorescence detection. The linearity, repeatability, and recovery of the method for seven amines (tyramine, putrescine, cadaverine, histamine, agmatine, spermidine, and spermine) were evaluated. This optimized method was applied to detect biogenic amines in squid and white prawn during refrigerated storage. Sensory analysis, pH value, and total volatile base nitrogen value were combined to evaluate the freshness quality of these two raw materials. Agmatine and cadaverine in squid, cadaverine, and putrescine in white prawn were the most obviously changed amines during the storage at two different temperatures, and these biogenic amines could be the effective quality indicators for the freshness of the raw aquatic materials.

No abstract