Water-hexane sorption in sunflower meals

Sorption equilibria of water and hexane in sunflower meals were determined at atmospheric pressure and temperatures from 50 to 95 degrees C. Adsorptio n-desorption experiments, for both individual vapors and water-hexane mixtu res, were carried out using a dynamic technique based on gravimetric measur ements with a Cahn electrobalance. The isotherms were fitted to the Guggenh eim-Anderson-deBoer sorption equation, and the heat of sorption was evaluat ed from experimental results. In the range of temperatures investigated, wa ter sorption was several times higher than hexane sorption, the differences increasing with solvent activity. The net heat of sorption that resulted w as significantly higher for hexane than for water. Water sorption isotherms were slightly affected by temperature, especially at water activities grea ter than 0.6. Some hysteresis was observed in water sorption at 50 degrees C, but it was practically negligible at higher temperatures. Hexane previou sly adsorbed in the meal did not affect significantly the sorption of water . On the contrary, water previously adsorbed in the meal increased the amou nt of adsorbed hexane.