EFFECT OF THERMAL TREATMENT ON THE RHEOLOGICAL PROPERTIES OF CARRAGEENAN GELS.

Carrageenans are sulphated polysaccharides obtained from red seaweeds. They play an important role due to their gelling, thickening and stabilizing properties, which are widely used in the food, cosmetics and pharmaceutical industries. In the commercial process of carrageenans, heat is generally employed during extraction and drying that can affect the polysaccharides' functional properties. Therefore, the aim of this study was to investigate the thermal treatment (75-115 °C for 15 minutes) on the rheological behaviour of k-, k/l-, i-carrageenan and furcellaran gels. All studied polysaccharides showed a storage modulus (G') vs. frequency dependence and can be categorized as a typical physically cross-linked network gel. No changes in gel strength values were observed with 2.5% (w/v) k-, k/l-, i- carrageenan gels during thermal treatment. However, 2.5% (w/v) furcellaran formed thermally unstable gels as the gel strength was decreasing with increasing the treatment temperature. The melting and gelling temperatures were decreasing with increasing the heat treatment temperature for all carrageenans while furcellaran was most affected by thermal treatment. [ABSTRACT FROM AUTHOR]