Water-sorption isotherms for corn starch and their model developments

In order to better dry, store and package corn starch and its products, the effect of temperature on the water sorption isotherm for corn starch should be determined, and a new sorption isotherm model including temperature and water activity should be developed. Adsorption and desorption isotherms for corn starch powders were determined at 30℃, 45℃ and 60℃ respectively by means of static-adjusting ambient humidity based on adsorption theory. Results showed that the isotherms of corn starch exhibited Type II, the sorption capacity decreased with the increase of temperature at constant water activity and equilibrium moisture content increased with the increase of water activity, sorption isotherm had an evident hysteresis over the entire range of water activity. A new sorption model of corn starch based on BP neural network was developed. The results of analysis showed that BP neural network model included temperature and water activity parameters, and its precision was better than other mathematical models.