The production process of corn germ

Today I will introduce to you the production process of corn germ, which is actually quite simple:

1. Clean up.

The corn germs recovered from corn grits are mixed with a lot of corn powder, broken powder and dandruff, and need to be screened with a double-layer vibrating screen. The first layer of the screen mesh is 1.5×1.5 mesh/cm to remove large impurities; the second layer is 4×4 mesh/cm to remove corn powder, broken grits and dandruff. If there are still a lot of germ crumbs in the sieve, 5×5 mesh/cm or 7×7 mesh/cm can be used to reduce the loss of corn germs. The corn germs recovered from corn starch are mixed with impurities such as dandruff and coleoptiles, and need to be rinsed several times with clean water in a shallow tray or trough. If the factory is equipped with a cyclone separator, the centrifugal effect generated by the cyclone can be used to separate the germs.

2. Dry.

Corn germs recovered in the process of making corn grits and corn starch contain a high moisture content after cleaning, and the enzyme activity is strong and it is easy to be reproduced by microorganisms, causing oil esters to deteriorate and become rancid, which not only affects the yield and quality of oil products, but also reduces the utilization value of cakes and dregs. In order to keep the freshness of corn germs during storage and transportation, the cleaned corn germs need to be immediately sun-dried or oven-dried until the moisture content drops below 10%.

3. Soften.

It is the first treatment for corn germ to produce oil. The moisture content of corn germ is adjusted to below 10% while being heated, and the plasticity of the germ is changed. Then the germ is rolled, and it can be rolled into a certain thickness without being easy to crush. Hot air dryer or hot steam roller dryer is commonly used for softening. When softening, the germ should not be treated at high temperature in a hurry to prevent premature denaturation of protein, which will cause the germ to lose elasticity and affect the rolling, steaming and oil pressing.

4. Roll the embryos.

After the corn germ is softened, it is rolled into thin sheets of 0.3 mm to 0.4 mm by a roller mill, which destroys the cell structure and shortens the oil path, making it easier to steam, fry and press the germ.

5. Steam and stir-fry.

The moisture content of the embryo material when entering the steaming and frying equipment is not less than 12%. After 40 minutes to 50 minutes, the temperature of the embryo material is finally raised to more than 100℃. The moisture content of the embryo material gradually decreases from 12% to 3%-4%, and the color of the embryo material gradually changes to brown-red. The aroma can be smelled but there is no burnt aroma. The embryo material is subjected to the dual action of steaming first and then frying in the whole steaming and frying process. At the same time, the moisture, temperature, plasticity and elasticity of the embryo material when entering the pressing are slowly adjusted and controlled, the protein is denatured, the cell colloidal structure is destroyed and the viscosity of the oil contained is reduced, which prepares the conditions for the extraction of oil from the embryo material.

6. Pressing.

There are three methods for oil production: pressing, extraction and water replacement. The equipment and production scale used in the pressing method can be divided into wood pressing, screw pressing and hydraulic pressing. Since the production of corn axillary bud oil is mostly carried out by small-scale and auxiliary workshops, it is most appropriate to use a screw oil press. The model can be determined according to the production scale. For larger-scale production plants, a 200-type screw oil press assembled with steaming and frying equipment can be selected. It has both steaming and frying, continuous operation, and easy operation. The steaming and frying of the embryo and the pressing of oil are completed in one set of equipment. When the temperature of the steamed and fried embryo reaches 115℃-120℃ and the moisture content is 2%-4%, it will directly enter the press for oil pressing. At this time, the room temperature needs to be maintained at 30℃-40℃. The embryo is initially fed with less material. After the press is running normally, the temperature of the pressing chamber rises, and then the material is fed, the oil and the cake are discharged evenly. The cake can smell the fragrance of the cake, the cake is solid, the surface is smooth, there are cracks on the back, and the oil is discharged normally. If the steaming and frying temperature is too low, the moisture content of the germ is too high, the cake is soft, the water vapor is very strong, the oil color is not right, it is white and bubbling, and the oil output is reduced. If the steaming and frying temperature is too high and the moisture content of the germ is too low, the cake color is too dark, the outlet emits green smoke and has a burnt smell, the oil color is dark, and the oil output is also reduced. For a normally operating press, the oil pressing speed is generally controlled at 8 rpm, the time the germ is pressed in the pressing chamber is 2.5 minutes, and the thickness of the cake is 5 mm-6 mm. The oil yield of corn germ extracted from corn grits is 22%-26%; the oil yield of corn germ extracted from starch is 25%-28%, and the residual oil rate in the cake is 5%-6%. The produced corn germ oil, unrefined and commonly known as "crude oil", has 0.3% moisture and volatile matter, 0.2% impurities, 6 acid value, 6% sediment, light yellow color, normal smell, and precipitation after heating at 280℃. "Crude oil" is not resistant to storage due to its high moisture and impurity content. It needs to be refined through hydration, alkali refining and deodorization to obtain high-quality refined corn oil.