Structural features and water sorption isotherms of carrageenans: A prediction model for hybrid carrageenans.

EXPERIMENTAL: water adsorption and desorption isotherms of kappa/iota-hybrid carrageenan (KIC) extracted from Mastocarpus stellatus red seaweed as well as commercial kappa-carrageenan (KC) and iota-carrageenan (IC) were obtained at several temperatures (5, 25, 45, 65°C). Spectroscopic and X-ray diffraction techniques allowed identifying the fundamental composition of above biopolymers. Crystallinity values (%) followed the order IC (25.4±0.6)> KIC (9.3±0.4)> KC (4.8±0.2), which nicely matched with the hygroscopic properties of the tested biopolymers (KC > KIC > IC) at each temperature. Sulphate content and sulphation degree of KIC were also intermediate. The experimental sorption data were successfully fitted using the two-parameter Caurie model, selected following a statistical analysis. A prediction model to estimate the KIC water sorption isotherms based on its individual disaccharides units content (%mol) (kappa- (73±4) and iota- (27±4)) and including the temperature effect was successfully developed.