Polysaccharide contents and sugar compositions of porphyran in dried sheets of nori

Abstract

  By the extraction of dried sheets of susabinori, Porphyra yezoensis, with 80% EtOH at 75℃, the solvent soluble pigments and low molecular weight compounds were removed. The decolorized nori samples were dried, and were crushed with a Wonder Blender to obtain fine powders. Constituent monosaccharides of the polysaccharides in the powders were liberated quantitatively by anhydrous mercaptolysis, as described previously. The liberated monosaccharide diethyl dithioacetal derivatives were trimethylsilylated and then analyzed by GLC. The derivatives of galactose, 6-O-methylgalactose, 3,6-anhydrogalactose, xylose, mannose, and glucose were detected in all nori samples tested. Individual polysaccharide contents were calculated from the amounts of corresponding component monosaccharides. Namely, porphyran contents were obtained from the sum of the amounts of galactose, 6-O-methylgalactose, and 3,6-anhydrogalactose, and xylan, mannan, and starch contents were obtained from the amounts of xylose, mannose, and glucose, respectively. Contents of the polysaccharides except for starch increased with growth of nori blade, and the increments in porphyran and xylose were significant. In addition, ratios of 3,6-anhydrogalactose and 6-O-methylgalactose in porphyran increased with prolonged cultivation period. It is apparent that the polysaccharide contents and the properties of porphyran respond to the growth of nori blade.