Moisture sorption isotherms and modeling for pre-cooked flours of pigeon pea (Cajanus cajans L millsp) and lima bean (Canavalia ensiformis) Original Research Article

The moisture sorption isotherms for pre-cooked flours of pigeon pea and lima bean were determined using the static method of saturated salt solution in a range of water activity from 0.20 to 0.97 at 18, 28, 38, and 48 °C and fitted by the Henderson, Chung and Pfost, and Ratti, Crapiste and Rotstein models. The moisture content of the material tested varied from 8% to 60% (dry basis). The agreement between experimental and predicted values is good for three models; nevertheless the Ratti, Crapiste and Rotstein (1989) model gave a better fit of the experimental data. The net isosteric heat of water sorption, estimated by applying Claussius-Clapeyron equation to sorption isotherms at mean temperatures of 23, 33 and 43 °C, was found to be different for pigeon pea flour and lima bean flour. The net isosteric heat of sorption for two flours increased with increasing moisture content and decreased with increasing temperature.