Evaluating and Recommending the Most Appropriate Pistachio Drying System Among Four Common Types of Dryers in Kerman Province, Iran

The present study was carried out in order to compare the effect of four types of conventional pistachio drying systems including diesel- and gas-fueled wagon and carriage dryers on the pistachio shell opening rate, shell damage, drying uniformity, storage shelf-life, pistachio quality, fuel consumption, energy efficiency, and economic efficiency. Two well-known pistachios types including elongated and round types were chosen for this study. The obtained results showed that: A) The rate of pistachios shell opening using a diesel-fueled wagon dryer was profoundly higher than those of the other systems due to its high drying air temperature (90 oc) and the thin layer of the moist product (20 cm) within the dryer. B) The wagon dryers led to less damage (around 39 percent) to pistachio nuts because of the absence of agitation. C) Generally, the energy consumption of wagon drying systems was lower compared with the carriage systems (around 50 percent). D) Higher drying uniformity was obtained using the gas-fueled carriage dryer due to an appropriate agitation. E) Dryer type and storage time up to 6 months, had no significant effect on the oil percentage, peroxide number, and pistachios quality. F) The gas-fueled wagon dryer had the highest economic profitability among the systems studied. G) The gas-fueled wagon dryer had the highest energy efficiency compared (around 15 percent) with the other systems. H) The pistachio types did not have a significant effect on the investigated parameters.