Evaluating adsorption isotherm and isosteric heat of freeze-dried pomegranate seed powder and Fitting the data with mathematical models

Experimental work was undertaken to obtain the adsorption isotherms of freeze-dried pomegranate seed powder. Moisture equilibrium data of pomegranate seed were determined using the static gravimetric method. Adsorption Isotherms were determined at 25، 40 and 60°C over a water activity range of 0. 11 to 0. 94. Six isotherm equations including GAB، BET، Iglesias and Chirife، Henderson، Smith، and Oswin were applied for analyzing the experimental data. The constants in the mentioned models were determined and correlated with temperature. The criteria used to evaluate the goodness of fit of each model were Correlation coefficient (R2)، Chi-square (χ2)، mean relative percentage deviation modulus (P) and root mean square error (RMSE). The results showed that the GAB equation gave the best fit to the experimental data. The net isosteric heat of sorption was determined using the Clausius-Clapeyron equation. The heat of sorption values of pomegranate seed powder were found to be large at low moisture content and decreased with an increase in moisture content.