Mathematical modelling of moisture sorption isotherms of local fish based snack from different manufacturers using BET and GAB models

Abstract

Fish cracker is a popular local fish based snack in Malaysia. The study of moisture sorption isotherm of fish cracker is essential to predict its storage and drying conditions by establishing its equilibrium moisture content (EMC) at specified conditions. By using static gravimetric method, moisture sorption isotherm of fish cracker was established at 30˚C, 40˚C and 50˚C within the water activity ranges from 0.04 to 0.80. The data were compared between two different manufacturers of fish cracker and it was found that the manufacturers gave no significant difference on the EMC of fish cracker. The predicted data by GAB and BET models were fitted to the experimental sorption data of fish cracker. The GAB model showed the best fit to experimental adsorption and desorption data for fish cracker of PNK Tanjung Dawai at 30˚C and for fish cracker of Perusahaan Hasil Laut Musliha at 40˚C respectively. The net isosteric heat of sorption of fish cracker was determined by using Clausius-Clapeyron equation and it was found that the net isosteric heat of desorption of fish cracker was higher than that of net isosteric heat of adsorption. GAB model was the best model in predicting EMC of fish cracker.