Dynamic study on the mechanism of gelation of carrageenans by ATR-FTIR spectroscopy at variable temperature

The high gelling ability of polygalactanes is not only due to their tertiary structure in double helices but also to the formation of aggregates. This step, which has been demonstrated to be very important in the gelation process, depends on the adjunction of cations in aqueous solutions of polysaccharides. However, the gel strength varies with the nature and the concentrations of the cations. In this work, we study solutions of kappa and iota carrageenans in the presence of Li⁺, Na⁺, K⁺ by ATR-FTIR spectroscopy between the room temperature and 80 degree(s)C. Differences due to the interactions of cations with polysaccharides are interpreted from the variations of the sulphate groups and the glycosidic linkages vibrations.