تعيين منحني هاي سم دماي وضعي رطوبت در دماهاي خشك كردن پسته

Determination of Pistachio (pistacia vera el) Moisture Desorption Isotherms Curves in Drying Temperatures

Pistachio is one of the most important horticultural products in Iran and its processing and packaging play major roles in exportation. Drying is a very important step in pistachio processing. In this step kernel moisture content decreases to 4-6 percent (d.b.), which is suitable for storage condition. The equilibrium moisture content (EMC) has important effects on drying time and kernel quality. In this research, pistachio moisture desorption isotherms were obtained at different drying temperatures (45, 60, 75, and 90°C) for two split Iranian pistachio varieties: Kalehghouchi and Fandoghi. For this purpose, static method and saturated salts were used based on COST-90 procedure. The results were evaluated by several models including: GAB, Smith, Henderson, Halsy and Oswin. The experimental results showed that for each variety, EMC values were reduced by increasing temperature. At different temperatures, GAB and Smith models gave better fitness for the data compared to the other models. Increasing temperature caused the reduction of mono layer moisture content in pistachio. Also, regression equations were obtained for estimation of mono layer moisture content at 45- 90°C for each variety.