WATER SORPTION ISOTHERMS AND AIR DRYING KINETICS OF FUCUS VESICULOSUS BROWN SEAWEED

Water sorption isotherms at 5, 25, 45 and 65C and air drying kinetics at 35, 50, 60 and 75C of Fucus vesiculosus seaweed were determined. Water desorption and adsorption isotherms were modeled using Halsey model. Monolayer moisture content, evaluated by means of BET model, decreased with increasing temperature. Thermodynamic properties (net isosteric heat, net equilibrium heat, differential and integral entropy) were also evaluated. Page model was used to fit seaweed drying kinetics in deep bed configuration. Seaweed mainly shrank at high moisture content during the induction and constant drying rate periods. The critical moisture content rose linearly with drying temperature (from 1.8 to 2.5 kg water (d.b.)(-1)). Diffusional model, assuming semi-infinite cylinder geometry, was employed for the drying kinetics modeling during the falling drying rate period for thin layer configuration. The corresponding effective coefficients of water diffusion rose with increasing temperature from 1.0 up to 2.8 X 10(-10) m(2)/s.