|Production capacity||500 Kg/hour|
These ovens have been specially designed for drying and roasting of dried fruits such as sunflower seeds, pumpkin seeds, almonds, hazelnuts, pistachios, peanuts, etc either natural drying or with salt. These roasting ovens can also be used to dry and roast other seeds, rice corn, and for most snacks.
These ovens have been designed to process solid products, most of them hygroscopic, where the steam tension is less than that of the water at the same temperature. The state and the tensions of the hygroscopic solid are altered with the contribution of the liquid or water that is added to it.
In the granular and porous solids, like Dried fruits, the water moves across the interstices, by virtue of forces or capillary tensions; if these tensions are exceeded due to factors such as excess of temperature, fit of time, boiling, etc., the capillary diffusion of the dampness in the solid will not be correct and it could remain trapped between the above-mentioned capillaries. It is well known, that dampness shortens the life of the product and accelerates its decomposition.
Drying and roasting system
The oven includes a chamber or heat source of thermal exchange to gas, diesel oil, and electricity. Through this chamber passes an air draught generated by turbines. This draught passes from the heating chamber to the drying and roasting chamber forming a semi-closed air circuit in the inside of the oven. The extraction of the dampness, as well as the contribution of clean air to the interior of the oven, is made by natural or forced shot of chimneys.
The above mentioned warm air penetrates through the following places:
-The orifices of the meshes that transport the fruits inside the oven
- The sides of the oven.
-The laterals of the oven
-The front and back of the oven, etc.
THE OVEN incorporates several moving belts made of metallic mesh in St. Steel placed one on top of the others, of such a way, that the first one of them receives the fruits from an in-feed hopper, placed in the top part of the oven, which discharges the product and turns them in the immediate belt below it and this one to the one below it and so forth until the product reaches the exit of the oven.
Every conveyor belt has a different temperature, being the lowest the first one and the highest the last one. This arrangement ensures that inside the oven the fruits are first dried, then dehydrated and finally they are toasted.
Drying at low temperature
The product enters the oven very humid, this way, the first belts that receive it, start drying it at a temperature below the boiling point of the water. This is a basic quality in any process of this nature. The boiling drags, together with the water steam, mass particles of the product submitted to it, as well as alterations in the coverings that are done to it.
Dehydrating at medium temperature
As the product dries off and its covering hardens. It advances through a few belts at increasing temperature, which submit it to a post critique drying speed and over the water boiling point . The capillary diffusion is not altered although the capillary pores begin their superficial contraction tending to close.
The product arrives on the last conveyor with valuable color tones. This conveyor is the one with maximum temperature and the one that finishes the closing process of the capillary pores. These will be more or less closed according to the final color tone required in the product.
This system allows the dried fruits to have a more natural flavor and color, this way clear differences with other drying systems (such as rotary ovens or platform ovens electric belt or tray ovens) can be observed.
In general, all these ovens transmit the heat by means of radiant waves or heat radiation, which attack the fruits from the exterior towards the interior. The only thing that is obtained by this method is that the first layers of the fruit are roasted more so that the center layers will be more toasted but this way the fruit remains damp (closing of capillary pores), obtaining a color and flavor that is too toasted.
The behavior of the fruits in the oven is completely opposite to the one that is obtained by the method of radiation, since the product is roasted from the inside out and this way it keeps its natural color and flavor.
This system makes it possible that delicate fruits, that can lose their top layer of skin, could be toasted without any difficulty, in their natural and salty variety. Without producing either heavinesses or spots in the fruits. In addition, this system obtains a major production that the systems used up to the date, a higher homogenization in the products to be dried or roasted and a minimal cost (of wastages, manpower), consumptions, performances, etc.)