SORPTION OF WATER-VAPOR BY K-FURCELLARAN AND CA-FURCELLARAN FILMS

Sorption of water vapour by films of the food polysaccharide furcellar an at 22, 35 and 50 degrees C in the vapour activity range 0.1-0.96 is reported. The sorption isotherm data are well described by the locali zed sorption model at low activities. At high penetrant activities, cl ustering of water is suggested by a Zimm-Lundberg analysis of the sorp tion data. Influence of Ca2+ and K+ cations on the sorption capacity, free energy and enthalpy of sorption is presented and discussed. Diffu sion coefficients of water within the polymer matrix are calculated us ing the long-time approximation for sorption kinetic data. The D value s are 5 x 10-(13)-7 x 10(-12) m(2)/s under the experimental conditions used. The values of activation energy are 32-34 kJ/mol for both Ca- a nd K-furcellaran.