Impact of pretreatment on the quality of soybean oil and meal

Soybeans are native to China and are grown all over the world. The main production area in China is the Northeast. Soybeans are edible oil and protein resources with high nutritional value. They can be used to make various soy products, brew soy sauce, press oil and extract protein. Soybean oil is one of the most commonly consumed edible oils at home and abroad. Soybeans have a high protein content and an oil content of about 20%.

Before entering the workshop to make oil, soybeans need to go through cleaning, crushing, peeling, softening, flaking, cooking. The quality of soybean pretreatment is related to the quality of soybean oil and soybean meal. In soybean oil production, the oil needs to be pre-treated before entering the oil press or extraction equipment. The purpose is to clean up impurities such as gravel, soil, grass clippings, etc. in the raw materials. On the other hand, it is to crush the oilseeds, change the shape of the oilseeds, and adjust the moisture of the oilseeds to make it a structural oil.

The following is the soybean pretreatment process:

1. Cleaning

Soybeans must first be cleaned and impurities removed. The mud, stones, stems and leaves, iron and moldy soybean grains carried in the raw soybeans are removed by screening, air separation, magnetic separation, specific gravity separation and other methods according to different physical properties. The cleaning equipment mainly includes vibrating screens, specific gravity stone removers, air suction separators, permanent magnetic drums, etc.

2. Crushing

If the cleaned soybeans contain low moisture, they can be directly crushed into 2-4 petals. If the moisture content is high, they need to be dried before crushing. Soybean peeling is required during the pretreatment process. Soybean peeling requires that the moisture content be reduced to a certain proportion first, and then the moisture is dried before crushing. This is conducive to the separation of bean kernels and seed coats. The bean coats contained in the crushed soybean grains are separated by a multi-stage aspirator;

3. Softening

Softening is an important pretreatment step before the flaking process. The conditioning equipment adjusts the oilseed to a suitable temperature and moisture. The texture of soybeans is hard. Softening can soften the texture, increase plasticity, improve oil production, and minimize the residual oil in the pressed cake.

4. Flaking

The crushed and softened soybeans must be rolled by the flaking equipment to make them into material embryos or raw embryos with the required thickness. The crushed soybeans fall into the feeding scraper of the flaking machine and are distributed to the double-roll hydraulic flaking machine to press the soybeans into thin slices. During the embryo pressing process, the soybean cell wall is broken by squeezing and kneading, releasing the oil wrapped in the cell, and pressing into thin sheets greatly shortens the distance of oil outflow, so as to improve the oil yield in the subsequent oil pressing process. The soybean oil after embryo rolling is steamed and fried, the heat absorption surface is increased, the heat absorption is uniform, and it is easy to absorb water.

5. Cooking

The process of turning the raw embryo after embryo rolling into mature embryo through wet heat treatment such as adding water, heating, and drying is called cooking. Cooking equipment mainly includes steaming and frying pans, which are vertical or horizontal. Vertical steaming and frying pans are more commonly used in large oil processing plants. When the embryo is steamed and fried, the dispersed oil in it absorbs water and heat, and gathers on the inner and outer surfaces of the embryo, which increases its oil yield under the same pressing pressure.