Thermodynamics of Moisture Sorption in Winged Bean Seed and Gari

Experimental data on sorption isotherms of gari and winged bean seeds were used to determine their thermodynamic functions (heat of vaporization, spreading pressure, net integral enthalpy and entropy). The heat of vaporization of both products reduced with increase in moisture content and approached that of saturated water at moisture contents of about 15%. Within the moisture content range of 2.0 and 18.0%, the net integral enthalpy and net integral entropy of gari were respectively higher and lower than those of winged bean seeds. The maximum net integral enthalpy for gari was 556 kJ/kg and was 335 kJ/kg for winged bean seeds. The difference in the values of the thermodynamic functions were attributed to the higher amount of oil/fat in winged bean seeds and the presence of gelatinized starch in gari.