moisture sorption isotherms for pistachio powder were determined by gravimetric method according to cost 90 project at temperatures of 15, 25, 35, and 40oc . maximum hysteresis level in sorption isotherms curve was observed at the range of water activity 0.2-0.7 . on the other hand hysteresis was diminished between adsorption-desorption isotherm curves when temperature reached 40oc. some mathem...