مرجع مقالات پسته مرغوب

1- Wagon dryer

Wagon dryer has a fan, oven, channel Iranian Pistachio and wagon-like wagons (Figure 1). The floor of the wagons is made of a mesh plate. This plate is located on a chamber with variable depth. The wagons are connected to the channel by tarpaulin or a clamped metal interface. Hot air is blown into the pistachio through the duct and through the pores of the lattice plate. These dryers are made in four and eight wagons. The eight-wagon type of these dryers has a capacity of drying 2100 kg of pistachios for pistachio cultivar of hazelnut cultivar with an accumulation depth of 18 cm. The disadvantages of this type of dryer are the force of the process in order to use labor to stir the product and the possibility of physical damage to the product and also the impossibility of uniformly lowering the moisture of pistachios to the desired level. The flow of the product is discontinuous and this type of dryer has a good separation capability, ie different cultivars can be dried without mixing. They are available in two types of gas burner and diesel and its fuel consumption is high and if we want to use its direct flame type, only the gas burner type has this capability and due to sudden changes in hot air temperature, we must use a thermostat or thermometer. Digital as well as gas control valve (electric or manual) adjust the amount of fuel. This type of dryer is a placeholder and if we have a lot of product for processing, we should consider a lot of space for this dryer.

2- Continuous double wall vertical dryer

In this method, the pistachio is located between the two inner and outer walls of the machine and is pushed down by gravity. The walls are latticed and hot air is blown into the products through the central space of the inner wall and directed outwards from the outer wall (Figure 2). Normally, two devices of this dryer are placed next to each other in series and pistachios enter the other after leaving one. This dryer does not require a worker. The space required for this type of dryer is low and energy consumption is optimal. In Iran, the problem of maintaining the uniformity of drying different layers in this technology is not well solved. This drying method is done in California due to the single digit of American pistachio (Kerman cultivar) because if we have different cultivars, it is not possible to use this dryer due to the mixing of cultivars. If this type of dryer is used, if the amount of product is less than the capacity of the dryer, we must use the common processing method or buy more.

3- Intermittent cylindrical vertical dryer

In this method, as in the previous case, the product is inserted between the walls of two interlocking coaxial cylinders, one of which has a radius of about 25 cm less than the other, and can use the force of gravity to route the wall from the bottom during drying. Slow (Figure 3). Disadvantages of this type of dryers include the impossibility of drying different varieties of pistachios continuously, although this type of dryer is not currently used in pistachio processing centers.

4- Continuous conveyor dryer: In this type of dryers, the product passes through a lattice conveyor where hot air is blown into the product from below. Paddles may facilitate the flow of pistachios forward. This type of dryer is made with a length of 22 meters and a width of 2.5 meters and three heat sources that provide temperatures of 80, 70 and 60 are placed along the dryer (Figure 4).

Burning gas or diesel is used to provide the required temperature for this type of dryer, and calculating its energy efficiency requires further research. It does not have good product resolution and is not suitable for low capacities. The space occupied by this dryer is not very large. For continuous drying, two silos must be used, one before drying to regulate nutrition and create a constant flow of pistachios into the dryer, and the other is a silo that performs aeration (by ambient air) to pistachios. And placed after the dryer.

Important indicators in the process of drying pistachios

- Changing the temperature and velocity parameters of air flow has a significant effect on the duration and drying efficiency of pistachios and the quality properties of dried pistachios, so that with increasing temperature, the amount of laughter increases and the number of free kernels increases (Table 1).

- In drying pistachios by aeration method, spots on the skin, the amount of aflatoxin and drying time are affected by factors such as the depth of accumulation of pistachios, the speed of air blown into the pistachios and the drying temperature.