Preparation and characterization of octenyl succinic anhydride modified agarose derivative

Agarose was successfully modified with octenyl succinic anhydride (OSA) and the factors affecting OSA modifying process were studied. The degree of substitution (DS) could be regulated from 0.02 to 0.21 by changing the reaction condition, simultaneously the molecular weight of the OSA-agarose (OSAG) varied from 342 kD to 483 kD. FT-IR spectrum of the OSAG at 1734 cm^-1 and 1576 cm^-1 revealed characteristic absorption peaks of the ester carbonyl groups (CO) and the carboxylate (RCOO^-), respectively. NMR spectrum of the OSAG suggested the main substitution occurred at the C-2 in the d-galactopyranose. The SEM image of agarose showed the porous network structure became dense and the fiber became thin after OSA modification. Compared with original agarose, the prepared OSAG showed novel physical properties including low gelling and melting temperature and high transparency. The remaining gelation ability and newly introduced amphiphilic character anticipate potential application as functional polysaccharide materials in foods.