Structure and Rheological Behaviour of Agar Extracted From Madagascar Sea Coast Algae

Abstract

Polysaccharide from an original red algae (Gelidium sp) was extracted with hot water, clarified, and precipitat- ed in presence of ethanol. NMR spectroscopic analyses and chromatographic separation after complete hydrolysis showed that this polysaccharide was composed predominantly of a repeating-unit based on 4-O-3,6-anhydro-α-L-galactopyranose and 3-O-β-D-galactopyranose confirming their agar nature. The Gelidium sp agar (representing 16 w % on the basis of dried crude algae) has a regular chemical structure and forms strong gels in aqueous medium. Its rheological behavior is examined as a function of polymer concentration and temperature.