The oil decolorization process is an indispensable step in the refining process. It is mainly used to remove impurities such as pigments, oxidation products, residual trace phospholipids and soap residues in oils to improve the color, stability and quality of oils. This process is essential for the production of high-quality, transparent edible oils.
Introduction to oil decolorization process
Purpose of decolorization:
Remove natural pigments in oils, such as chlorophyll, carotene, anthocyanins, etc.
Remove oxidation products in oils to prevent rancidity.
Remove trace impurities in oils, such as phospholipids, metal ions, soap residues, etc., to prevent oil discoloration and oxidation.
Decolorization principle:
Through the physical adsorption of the adsorbent, the pigments, oxidation products and other impurities in the oils are adsorbed onto the decolorizer, so that the color of the oil becomes lighter or transparent.
Oil decolorization process
Degumming and deacidification:
Before decolorization, oils are usually degummed and deacidified to remove most of the phospholipids and free fatty acids in the oils. Otherwise, these substances will affect the adsorption effect of the decolorizer.
Heating decolorization:
Oil usually needs to be heated to 90°C~110°C before decolorization. The choice of temperature depends on the type and quality of the oil. At high temperature, the decolorization effect is better, the adsorption capacity of the adsorbent is enhanced, and the fluidity of the oil can be improved and the adsorption of impurities can be promoted.
Adding adsorbent:
Common decolorizers include activated clay, activated carbon, etc. These adsorbents have a large number of microporous structures and a large specific surface area, which can effectively adsorb impurities such as pigments and oxidation products in oils.
Activated clay is used to remove colored substances, metal ions, oxidation products, etc. in oils; activated carbon is mainly used to adsorb residual pigments and odors.
The amount of adsorbent is usually 0.1%~2% of the weight of the oil, depending on the quality and color requirements of the oil.
Stirring adsorption:
After the adsorbent is added, the oil and the adsorbent are fully stirred under vacuum or normal pressure to make the adsorbent fully contact with the oil. The stirring time is usually 20~30 minutes. If the stirring time is too short, it will affect the decolorization effect, and if it is too long, it may cause the adsorption saturation of the adsorbent and the adsorption effect will decrease.
Filtration separation:
After the adsorbent absorbs the impurities, it is necessary to separate the adsorbent from the oil through the filtration system. Commonly used filtration equipment includes plate and frame filter, vacuum filter, etc. There should be no residual adsorbent particles in the filtered oil to ensure the transparency and purity of the product.
Subsequent processing:
The decolorized oil will enter the deodorization process to further remove the odor and volatile substances in the oil, and ensure the taste and storage stability of the oil.
Introduction to oil decolorization equipment
1.Decolorization tank:
Function: The decolorization tank is the core equipment in the oil decolorization process, which is used for the mixed reaction of oil and adsorbent. The decolorization tank is usually equipped with a heating and vacuum system to ensure the decolorization reaction under suitable temperature and vacuum conditions.
Main features:
Equipped with a heating device to ensure that the oil is heated to the specified temperature.
The vacuum system can prevent the oxidation of the oil and avoid thermal damage at high temperature.
The stirring device can ensure that the adsorbent and the oil are fully mixed to improve the decolorization effect.
2.Plate and frame filter:
Function: Used to filter the decolorized oil and separate the adsorbent and impurities from the oil.
Main features:
Use filter plates and filter cloths to separate solid adsorbents to ensure the purity of filtered oil.
Simple structure, easy maintenance, suitable for small and medium-sized oil processing enterprises.
3.Vacuum filter:
Function: Use the pressure difference under vacuum conditions to separate the decolorizer from the oil, which is widely used in large-scale oil production lines.
Main features:
Filtering under vacuum can effectively prevent the oil from contacting the air during the filtration process and causing oxidation.
Fast filtration speed, high separation efficiency, suitable for continuous production.
4.Activated clay conveying system:
Function: Used to accurately convey activated clay or other adsorbents to the decolorization tank. The system is usually equipped with a metering device to ensure that the amount of adsorbent added is accurate and stable.
Main features:
Precisely control the delivery and addition of adsorbents to ensure the consistency of decolorization effect.
Suitable for large-scale continuous production.
5.Continuous decolorization equipment:
Function: Used for continuous decolorization process in large-scale oil production. The equipment usually consists of multiple decolorization tanks and a filtration system to achieve continuous decolorization of oil.
Main features:
Suitable for large-scale industrial production with high efficiency.
High degree of automation reduces manual intervention.
Factors affecting oil decolorization process
Temperature:
When the temperature is too low, the oil has poor fluidity, and the contact between the adsorbent and the oil is insufficient, which affects the decolorization effect; if the temperature is too high, the oil may oxidize or deteriorate in quality. Therefore, the general decolorization temperature is controlled between 90°C and 110°C.
Amount of adsorbent:
The amount of adsorbent directly affects the decolorization effect. Too little amount may lead to insufficient decolorization, and too much amount will increase the cost and may affect the quality of the oil. Usually, the amount of adsorbent is controlled at 0.1%~2% of the weight of the oil.
Vacuum:
Under vacuum conditions, the oil is isolated from the air, which can effectively prevent the oxidation of the oil and improve the decolorization efficiency. Generally, the vacuum degree is controlled above 90kPa.
Stirring time:
If the stirring time is too short, the adsorption is insufficient, and if it is too long, the adsorbent may be saturated. Therefore, the stirring time is usually controlled at 20~30 minutes.
Advantages and Challenges of Oil Decolorization Process
Advantages:
Improve oil quality: Decolorization can significantly improve the color of oil, making it more transparent and of higher quality, which is suitable for market demand.
Remove impurities: The decolorization process can not only remove pigments, but also remove oxidation products and other trace impurities in oil, and extend the storage period of oil.
Widely used: Applicable to various edible oils, such as soybean oil, palm oil, sunflower oil, olive oil, etc.
Challenges:
Adsorbent loss: The adsorbent needs to be replaced regularly during use, which increases production costs.
High temperature control requirements: Temperature fluctuations may cause unstable decolorization effects, so the equipment must be able to accurately control the temperature.
Environmental requirements: The decolorization process needs to be carried out in a vacuum environment to prevent the oil from oxidizing at high temperatures, which places high requirements on the vacuum system of the equipment.
By reasonably selecting adsorbents and controlling decolorization process parameters, the color and quality of oil can be effectively improved to meet market standards.