History of cashew processing:

In the early twenties of the 20th century India had cashew nuts and exports. In 1925 India was considered as the exporter of cashew nuts.

Before the Second World War scientific and technological researches in the field of cashew processing were carried out, especially in production lines.

Currently, the technology used in the processing of cashew can be divided into processing by heat treatment technology and use steam. Also considering the level of mechanized division: manual processing and mechanical processing.

Some manual cashew processing schemes are available in India and some other countries


Manual processing:


Whole packed to 85%
Consumes cashew nut units for a low unit of product
Limited investment in equipment construction and procurement, rapid return on investment

Labor productivity is low
Use too many common labor
Therefore, manual processing is only suitable for areas where there are many common and manual labor.

In the early 1960s, a number of mechanical processing systems were introduced: the Oltremare (Italy) and Shock system. Sturtevant - Fletcher London made.

Mechanical processing chart

Processing cashew nuts by line:

Process of making products - cashew kernels include the following basic stages: first stage is raw material reception, drying - storage, preliminary size classification, cleaning, oiling or steaming, cutting, drying - processing, peeling, sorting, fumigation, screening - packaging - vacuuming, packaging - labeling and finally preservation - distribution and quality control. Each production step has a certain impact on the finished product and directly or indirectly affects the finished product in terms of quality, including food safety. Therefore, all stages of the production process must be strictly adhered to, strictly technical in order to ensure the stability, safety and the best product. Each stage has a certain meaning, decisive to the quality of products and prestige of the company producing products - cashew kernel.

Here are the main stages of the chain:

Preliminary size

Preliminary sizes are classified into 3 types: large, medium and small for a suitable moisture content for each particle size so that the desired particle size can be achieved.

 Clean sandy soil in cashew nut shell

This work is especially needed when applying oil shake technology. If not removed, sandy soils will deposit on the heat exchanger surface, causing local heat to overheat and cause For damaged equipment, sandy soils are used to thicken the oil quickly, preventing the bark from escaping during the panning process, which is commonly referred to as "oil spilling."

The case of steam treatment, sandy soil ... also stick to the shell will be mixed with oil when pressed shell for oil shell makes it difficult to refine oil and increase production costs.


Seeds before the oil rinse should be humidified to increase the initial humidity from 10% to 15-25% (usually 15-18%).

Moisture is actually adding water to the cashew nut.

Important impact of moisture:

Water infiltrates the shell to produce a mixture of shell oil and water, when the oil mist encounters high temperatures (180-200 degrees Celsius) suddenly the water in the mixture goes into a boiling-up state that breaks down the cells. Contains oil to allow the oil to drain easily and to cause the shell to swell to create a gap between the shell and the core.
 Thanks to the humidity increase will be more flexible, during the process of not losing gold and break when passing through the next shredding.
Can be moistened in one of the following ways:

Watering: Cashew kernels in piles or into wells with drainage holes and then watered several times (usually 1 hour irrigation), between the humidification. The number of times to irrigate depends on the initial moisture content, the size of the sample, the size of the shell, the thickness of the shell, and the storage time of the seed. Moisturizing the way watering takes time but less moisture.
Water immersion: the seeds are immersed into the water tank until the desired moisture level is reached (or drained) to drain. Soaking time depends on the condition of the cashew nuts as well. Moisturisation by soaking method shortens the wetting time compared to watering but is prone to over-humidity.
Mix well just soak the seeds: soak the seeds in water for some hours and then drain the water to drain some more water to adjust the moisture of the beans to meet the requirements.
Grain treatment (steamed) for 10 to 15 minutes.
When moisturizing, pay attention to:

Moistened water should not contain iron ions.
The water temperature does not exceed 30 degrees Celsius.
Do not allow water to penetrate the silk shell, because if iron is present in the water, it will react with the polyphenols of the silk shell to create bluish-blue complexes, which can cause patches on the surface of the white core.
   4. Heat treatment.

Heat treatment (roasting)

Using heat to make the shell of the cashew to swell, cracking out to oil the inner shell out and at the same time create a gap between the shell and the core, when the kernel shell is not broken shell and does not get dirty oil shell. There are two methods of roasting

Simple direct ranged - also known as combustion
Place the cashew nuts in a rotating bin and then heat it red with the open flask turning the barrel, the oil in the flask and burning fire. Due to the combustion of the shell oil that keeps the temperature of the barrel unaltered. The rotary bin is rotated manually for 2-4 minutes while the seed is still burning using a ash coating to extinguish and absorb the remaining oil on the surface of the seed coat and then through the cuttings. The method of cutting has the advantage of shearing speed and high percentage of intact but with disadvantages: loss of shell oil recovery, work environment is polluted by the smoke of burning shell oil to burn eyes. throat and less labor safety, product quality is low because the human being is almost yellow at the top. Currently less burning method is used.

Ranged in CNSL shell oil - also known as oil.
Oil skimming technology is widely used. Cashews were put into barrels chemical humidity (tanks) containing CNSL shell oil was heated to 180-200 0 C. Duration of cashews in oil (time perturbed) lasted 1-3 minutes depending size sing. During the shading of the seed coat, the cracking of the bird's legs due to the water vapor in the shell is removed, thanks to these cracks the oil in the shell escapes, causing the CNSL oil level in the tank to rise and be removed continuously during the cup. oil. After oiling, the seeds are passed through a centrifuge flask to remove all the oil from the shell and stick to the surface of the seed coat and cool it through the shredding process. In case the CNSL oil used to fry is too thick by centrifugal oil scrape is still attached to the seed coat can be mixed ash kitchen to the kitchen ash absorb all the oil to this stick.

The oiling process is determined to be technically achievable when at least 50% of the oil contained in the shell is removed, the surface of the seed is dry without oil, Birds, grasping seeds are light and feel when shaking between the shell and the kernel has a gap.

For good quality cashew nuts, ensure the following specifications:

Moisture content of grain when added to the chill 15-18%.
CNSL oil used for congealing must be of good quality (liquid), without mechanical impurities. The oil / grain ratio from 20/1 to 50/1 (preferably 50/1) means that for 1 kg of cashew nuts, 50 kg of shell oil is required to keep the congee temperature constant throughout the process. Hello.
The temperature of the congee is kept at 180 - 200 o C, the congee duration is 1 - 3 minutes depending on the size and moisture of the seeds.
However, these technical parameters work together so it should be adjusted and coordinated appropriately while the newly acquired product is good quality. For example, when the seeds are dehumidified without adjusting the temperature and the time of frying, when the seeds are chilled, they will be too dry (dry) and yellow, the peel of the silk shell is poor, resulting in the removal of the peel and the peeling of the silk Increased crack multiplication and lower kernel quality. If the seeds are too moist, and if they do not change the technique, the beans will be susceptible to oil contamination (high temperatures, high humidity will create conditions for chemical reactions such as oxidation reactions. hydrolysis ... produces new products: peroxides, free fatty acids in the nucleus) and has a watery yellow color, the rate of human experience is greatly reduced.

Treatment measures when the problem occurs:

 Moisture-deficient nuts:
CNSL oil must be used to ensure the quality of the cake.
Maintain the temperature of chao - Shorten the chao time; or lower the temperature of the congee keeping the temperature of the congeal.
 Excess moisture:
Only use CNSL oil to guarantee quality
Raise the temperature of the congee - keep the congee time constant; or keep the chao temperature - prolongs the chao time.
Compared with burning, the oil has many advantages:

Recovery of shell oil (at least 50% of shell oil in shell), high quality of product obtained (retain color and without CNSL shell oil).
Oil can be handcrafted (dipped in batch) or mechanized and fully automated.
Workplace environment is non-toxic, clean and safe.
Heat treatment is usually carried out at high temperatures but can also be performed at temperatures lower than 100-120 ° C if the moisture content of the cashew nuts is adjusted accordingly, called mild drum roasting. and mild oil bath roasting.

Hand-made oil-bathing equipment is very simple (see Figure 22). The metal-heated oil reservoir is heated directly to the bottom of the tank to raise the shell oil temperature to 180-200 ° C. put in a basket made of iron grids and recognized dip baskets directly and oil tank and kept in the oil for a period of time as prescribed and then take the basket out the grain through the centrifuge to clean the shell oil clinging to the shell Or removed to be mixed with ash to cook the ash aspirate all the oil clinging to the shell. Using manual oil heaters, laborers are very hard, hot, toxic by the oil vapor from the oil tank, the risk of fire is very high when oil reservoir is very easy to oil down to the fire.

 1. Steamer using 165-170 o C (steam pressure 120 psi ≈ 8.76 kg / cm 2 )

Steaming: steam for 10 - 15 minutes to warm the pot, stop feeding 320 kg of cashew nuts (7) and then steam at 120 psi for 30-45 hours. minute. Let 10 let the temperature in the autoclave uniformly and then remove the cashew via the exit door (5) the thin load to cool. During a 10-minute steady discharge of condensate over the drain valve (4). Allow seeds to cool for at least 24 hours before cutting.

2. Animated.

Here we introduce the method of sedimentation can overcome the disadvantages of static method. This method was developed by a group of engineers led by Engineer Tran Van Sum of Binh Dinh Vegetable Oil Joint Stock Company. Other static methods are static methods where a screw-type steamer is used. Raw nuts are not soaked in the water as in the semi-autoclave method but will be steamed. The process of gravitation takes place continuously without interruptions such as static steaming.

The essence of the solution: 
Use saturated steam to continuously grind the cashew nut: raw nuts move continuously from the inlet until they come out of the steaming device. It is this continuous movement that allows the cashew nuts to be continuously exposed to relatively saturated steam in the same degree of intensity, intensity and time. Thus, for a certain material (the same size, density and humidity), the moisture content of mechanical changes after autoclaving is about the same, Particles are hard as static, intermittent

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