Moisture sorption characteristics of tropical fresh water crayfish (Procambarus clarkii)

Moisture sorption characteristics of crayfish (Procambarus clarkii) were investigated at 25E, 30E, 40E, and 50EC using gravimetric method and the results analyzed according to various sorption isotherm models. The heats of moisture adsorption and desorption were estimated from equilibrium sorption data using the Clausius–Clapeyron equation. Equilibrium moisture content decreased with increase in temperature but increased with increase in water activity. Both adsorption and desorption isotherms were sigmoidal in shape (type II). The Henderson, GAB and Oswin equations provided good fit to experimental data (<10%RMS) for adsorption and desorption. The heats of desorption were higher than the heats of adsorption, indicating a significant hysteresis in moisture sorption by crayfish. Net isosteric heats of adsorption and desorption varied from 21.1 to 2.4 kJ/mol and 28.9 to 3.5 kJ/mol respectively while entropy of adsorption and desorption varied from −0.053 to −0.006 kJ/mol °C and −0.076 to −0.009 kJ/mol °C respectively within moisture contents range of 2.0 to 12.0 g H2O/100 g solids.