Studies on equilibrium moisture absorption of kappa carrageenan

This study describes investigation of moisture sorption behavior of Carrageenan at 10, 20 and 30°C under different relative humidity, in the range of 23 to 96 percent using gravimetric method. The equilibrium moisture uptake data, thus obtained, were fitted to three well known three sorption isotherm models, namely GAB, Halsey and Oswin models using non-linear least square method. The well-known GAB model best interpreted the equilibrium data in a satisfactory manner. The monolayer moisture content Xm, as determined from GAB model, was found to be 31.72 x 10^-3, 43.60 x 10^-3 and 17.41 x 10^-3 kg kg^-1, db at 10, 20, and 30°C. The isosteric heat of sorption (qst) was determined using Clausius-Clapeyron type equation. The uptake data was also used to determine isokinetic temperature Tβ (301.7 K) and harmonic mean temperature Thm (292.82 K). The enthalpy-entropy compensation theory indicated that moisture sorption process was enthalpy driven.