Soybean Oil Processing

Soybeans Cleaning

Soybeans can be mixed with impurities during harvest, transportion and storage. Although the soybean is usually cleaned before storage, it will still contain a small number of impurities after the initial cleaning, which cannot meet the requirements of soybean oil extraction. Therefore, soybeans have to be further cleaned after entering oil mill factory to reduce its impurity content to the range required by sobean oil extraction so as to ensure the effect of the oil production process and quality of final soybean oil. Cleaning methods include screening, air selection, specific gravity destoning, magnetic separation, dust removal, etc. The cleaning of soybeans usually requires an array of seeds cleaning machines to remove all the impurities. Sometimes, it doesn't require many unites.  

Soybean Moisture Conditioning

The moisture affects the physical properties of soybeans, such as elasticity, plasticity, mechanical strength, thermal conductivity and tissue structure, which directly affect the effectiveness of soybean oil processing. Moisture also has an impact on the activity of various enzymes in soybeans, which can change the nature of certain components in soybeans, which in turn affects the quality and yield of the soybean oil and its by-products. If the moisture content is too high, soybeans will be dried, usually by convection drying and conduction drying. If the moisture content is too low, it is humidified. Generally, saturated steam and water are mixed and sprayed onto the soybeas that is being transported, which can achieve a better wetting effect and a shorter time for moisture homogenisation.

Soybean Crushing

Before soybean flaking, large soybeans must be crushed into a certain particle for flaking. Soybean crushing increases the surface area, which facilitates the transfer of temperature and moisture when softening, thus improve softening effect. The requirements for soybean crushing are particle size uniformity, no oil, not into a group and less powder. The standard for soybean crushing is 4~6 petals, and power control at no more than 10%~20% mesh. If moisture content is too high, soybeang are not easily crushed and easily flattened, can has oil, which leads unsmooth and low output; Otherwise, the oil-containing powder is easy to adhere together to form a group. Commonly used crushing equipment are rod-toothed crushers, hammer crushers and disc shellers. 

Soybean Softening

Softening is to improve the elasticity of soybeans by adjusting the moisture and temperature of soybeans, so that it has the best conditions for flaking, reducing the powder and sticky roll phenomenon and ensuring the quality of flakes. Softening is mainly used for oilseeds with low oil content, low water content and high shell content with poor physical plasticity and hard texture. Oil content of soybean is low, poor plasticity, so it is generally softened before flaking. Flaking temperature should depend on the level of moisture content of soybeans. Soybean moisture for 13% to 15%, softening temperature is usually mastered in 70 ~ 80 degrees, softening time 15 ~ 30 minutes. Commonly used softening equipment are layer-type softening pot and drum softening pot.

Soybean Flaking

Flaking is to take use of mechanical action to make materials from the granular sheet into flake. The purpose of flaking is to destroy the cellular organisation of materials, to increase the surface area, to shorten the distance of the oil flow, to facilitate the extraction of the oil and to improve the evaporation effect. Flaking is the key to pretreatment and is related to the yield and quality of the oil. The key to soybean flaking lies in the operation of the flaking machine. In order to ensure the quality, the moisture and temperature of the material before flaking should be strictly controlled. Generally, soybean flaking thickness is 0.3mm or less. The flaking equipment can be divided into two categories: inline and flat mills. 

Soybean Extruding

Soybean extruding is the process of using extrusion and puffing equipment to convert crushed, flaked or whole oilseeds into porous puffed pellets. Extrusion is a high temperature, short processing process. Commonly used soybean extruders have single screw, twin screw two types, according to the extrusion of moisture content can be divided into wet, dry extrusion two methods. Generally speaking, in the extrusion process, the extrusion temperature can reach about 110 ~ 200 ℃, the residence time in the extruder for 1~3 mins, shortly 5~105 sec. The most important function of soybean extruding is to destroy cell structure for easy oil extraction, blunt all kinds of enzymes, improve the oil yield, increase oil output and reduce solvent loss. 

Soybean Oil Extraction – Leaching

This process is mainly using solvents that dissolve fats and oils to extract the fats and oils from soybean through wetting and penetration, molecular diffusion and convection diffusion. The basic elements in this process are solvent and soybean materials as well as the leaching method and process parameters. The type of leaching equipment is generally divided into batch and continuous. According to the leaching method, it is divided into immersion, infiltration and mixed. Each leaching equipment can be divided into many types based on its structure. And, Flat rotary extractor and ring type drag chain extractor features high efficiency, advanced technology and wide application. But its cost is higher. 

Crude Soybean Oil Refining

Crude soybean oil is generally defined as oil extracted by solvent extraction or pressing process that contains certain impurities that are not suitable for consumption (or industry). The main component of crude soybean oil is a mixture of glycerol triglycerides (neutral oil) and non-glycerol ester substances (impurities). Soybean oil refining is to add edible phosphoric acid, sodium hydroxide, decolourisation active white clay and other process auxiliaries, after a series of processes to remove impurities and components affecting the colour, stability and flavour, to improve the quality, flavour and storage stability. Tyical soybean oil refining process is degumming, deacidification, decoloration, deodorization.

Final Soybean Oil Packaging