Chemical characteristics and gelling properties of agar from two Philippine Gracilaria spp. (Gracilariales, Rhodophyta)

摘要: The chemical structure of agars extracted from Philippine Gracilaria arcuata and G tenuistipitata were determined by NMR infrared spectroscopy. Agar with alternating 3-linked 6-O-methyl-β-D-galactopyranosyl 4-linked 3,6-anhydro-2-O-methyl-α-L-galactopyranosyl units was isolated G. arcuata, while the agar possesses regular agarobiose repeating unit partial methylation at 6-position Dgalactosyl residues. Both exhibit sulphate substitution varying positions in polymer. Chemical analyses reveal higher 3,6-anhydrogalactose lower contents alkali-modified than native both samples. Also, alkali modification enhanced gel strength syneresis. Native produces a viscous solution (2000 cP 75 °C) high gelling point (> 60 that forms soft even after (gel strength: < 300 g cm−2). On other hand, exhibits qualities typical most agars.