Peanut Oil Production

Peanut oil production

1. Raw material screening and cleaning

Peanut raw materials need to be strictly screened to remove impurities (such as stems, leaves, sand and gravel, metal fragments, etc.). Vibrating screens, magnetic separators and other equipment are usually used to ensure the purity of the raw materials. The moisture content of washed peanuts needs to be controlled at 7%-9% to facilitate the subsequent red skin removal process.

2. Red skin removal and crushing

Peanut red skin contains tannins and other substances that will affect the color of the oil. It needs to be removed by a friction peeling machine or an airflow peeling machine (the peeling rate is generally 85%-95%). The peeled peanut kernels are crushed into 4-6 petals by a crusher to increase the surface area and provide raw materials for subsequent steaming and frying.

3. Steaming and frying (tempering treatment)

The crushed peanut kernels enter the steaming and frying pan and are heated at 105-115℃ for 20-40 minutes. This process can destroy the cell structure, reduce the viscosity of oil, and fully denature the protein, thereby increasing the oil yield. After steaming and frying, the material temperature rises to 65-75℃ and the moisture content drops to 4%-6%.

4. Pressing or leaching

Pressing method: Use a screw press for physical pressing, which is divided into pre-pressing (residual oil is about 12%) and full pressing (residual oil is 5%-6%). The crude oil after pressing needs to be filtered to remove the cake residue.

Leaching method: Use n-hexane and other solvents to extract the pre-pressed cake, and recover the solvent by evaporation and stripping, and the residual oil can be reduced to less than 1%. Peanut oil is particularly suitable for low-temperature leaching process.

5. Crude oil refining

Peanut crude oil contains impurities such as phospholipids and free fatty acids, which need to be purified through the following steps:

Degumming: Add water or phosphoric acid to hydrate the phospholipids and then centrifuge.

Deacidification: Add alkali (NaOH) to neutralize free fatty acids, generate soap stock and then remove it.

Decolorization: Use activated white clay to adsorb pigments (especially aflatoxin).

Deodorization: Distill to remove odor substances under high temperature (210-230℃) and vacuum conditions.

6. Finished oil processing

The refined peanut oil is cooled, crystallized and filtered (the temperature needs to be specially controlled in winter to prevent solidification), and then tested for key indicators such as aflatoxin and acid value. After passing the test, it is stored in nitrogen. High-quality peanut oil usually retains some aromatic substances, and some products are winterized to remove high-melting-point glycerides.