Design, construction and evaluation of a multipurpose machine for pistachio processing

Iran is the largest producer of pistachios in the world, and many researchers are studying on pistachios in the world. Most of the country's pistachio farmers are small farmers and for economic reasons they are often forced to sell their products at low prices to the companies that have machines for processing and decreases their incomes. Therefore, after construction and optimization of the device, its capabilities for processing (peeling, washing and drain or desorption of moisture) were evaluated in two different treatments. Power consumptions were measured by a digital Watt Meter. In treatment (A), the rotational speed of the outer abrasive shelf was less than the interior abrasive shelf but in treatment (B), the rotational speed of the outer abrasive shelf was more than the interior abrasive shelf. Average power consumption of the outer abrasive shelf was low, when its rotational speed was less than the inner abrasive shelf. The results showed that the average power consumption of the internal shelf was 1.33 kW in treatment (A), although its amount was reduced to 0.71 kW in the treatment (B). The average power consumption of the internal shelf in two treatments (A) and (B), were 0.54 kW and 0.73 kW 73/0, respectively, which indicates that in peeling process, the participation of internal abrasive shelf was more in treatment (B).The results also show that the amount of perfect peeled pistachio nuts in treatment (A) was 57.1 % and increased to 66.7% in treatment (B). Also, the amount of intact nuts (not peeled) in treated (A) was 22.9 % that decreased to 2.8 % in treatment (B). The results showed that in the peeling process, the performance of the machine is higher when the rotational speed of the outer abrasive shelf was more than the inner abrasive shelf. After peeling, washing process was carried out by fixing the outer shelf and running the internal shelf by slow speed. After washing process, device performance for removing the moisture was evaluated.Peeled pistachios were divided into four equal parts and then both the internal and external shelves were rotated in the same direction (against the cutting blades), with frequencies of 40, 50, 55 and 60 Hz for 15 minutes. Peeled pistachios attached to the internal side of the outer shelf by help of centrifugal force and rotated with it. The additional moisture was removed due to the high peripheral speed and consequently hit the wet nuts with the air. considering the radius of the outer shelf (0.4 m) and the transmission ratio of electric motors to the shelves (4:1), the peripheral speed of the wet nuts during the moisture removing process for frequencies of 40, 50, 55 and 60 Hz, were, 25.13, 31.42, 34.56 and 37.70 meters per second, respectively. After washing, the moisture content of the pistachio nuts was68.7 % dry basis. After the moisture removing process, the amount of moisture content of the nuts at frequencies of 40, 50, 55 and 60 Hz % decreased to 53.44%, 51.28%, 50.79% and 48.58% respectively. Increasing the rotation frequency increased the peripheral speed of the shelves and so moisture removing process increased. The results showed that the machine can get surface moisture of the pistachio and moisture content can be well absorbed after washing the product and increase product shelf life.