Investigation of pistachio (Kalleh Ghoochi v.) drying kinetics in a new intelligent rotary dryer under vacuum

Pistachio plays an important role as exportation of Iran. The method of drying process has a remarkable influence on the quality of dried products. There are various methods for drying pistachio; however, choosing a suitable method of drying depends on reliability, healthiness and rapids. In current research, the effect of temperature in three levels of 40, 50 and 60°C and rotational speed of the dryer agitator in three levels of 5, 10 and 15rpm on reduction rate of drying period and drying kinetics of a common Iranian pistachio (Kalleh Ghoochi v.), in a new intelligent- vacuum rotary dryer, was investigated. This dryer was consisted of a cylindrical chamber and a twin electrical heater which dried products in a vacuum medium. The experimental data was analyzed in a statistical software "SPSS 10 " In accordance with the results, temperature and rotational speed of the agitator had a significant effect on drying period. When temperature and speed were 60°C and 15rpm respectively, drying period was short and equaled 185 min, but in temperature of 40°C and speed of 5rpm, drying period was long and equaled 325 min. Increasing the temperature also increased the rate of drying significantly. Results indicated that increasing temperature from 40°C to 50°C caused 25% decrease in the drying period and increasing temperature from 40°C to 60°C caused 39% decrease in drying period.