Chemical and rheological characterization of the carrageenans from Hypnea musciformis (Wulfen) Lamoroux

This work reports a chemical and rheological study of the carrageenans from Hypnea musciformis, a red seaweed commercially known for its production of x-carrageenan. The polysaccharides were extracted with water both at room temperature and at 90 degrees C: the yield of the latter was about six times larger than the former. Fractionation with KCI yielded a large proportion (50-67%) of a precipitate with 0.125 M of this salt for both extracts, with characteristics of a nearly pure x-carrageenan, as determined by methylation analysis and NMR spectroscopy. Smaller amounts of fractions precipitating at higher concentrations showed a basic x-carrageenan structure, but included some L-carrageenan diads. The KCI-soluble polysaccharides showed a larger complexity, containing n- and L-galactans or OIL-hybrids. Some differences in the rheological properties of these carrageenans have been found. Although all KC1-precipitating polysaccharides form true gels at 10 degrees C in presence of KCI, those extracted with hot water form stronger gels than those extracted at room temperature. Both purified x-carrageenans show lower gelling and melting temperature than the whole polysaccharides from which they were originated. (C) 2013 Elsevier Ltd. All rights reserved.