Pressing and Solvent Extraction Methods in Soybean Oil Production

Soybean oil is one of the most commonly used cooking oils and the most produced edible oil globally. It comes in various types, categorized by the kind of soybeans, such as crude soybean oil and genetically modified soybean oil, and by processing methods, such as pressed soybean oil and solvent-extracted soybean oil.

Types and processing methods of soybean oil:

1. Processing soybean oil for oil production and feed use:

In this process, the common solvent extraction technique is used. After cleaning, peeling, crushing, softening, flaking, and expanding, the soybeans are sent to extraction equipment to obtain oil. The extracted soybean meal, after regular desolventizing, is suitable for animal feed. However, high-temperature desolventizing denatures the protein in the meal, making it suitable only for feed and not for isolating protein. The extracted mixed oil is refined through steps like degumming, neutralizing, decolorizing, deodorizing, and dewaxing to produce soybean oil.

2. Producing low-denatured soybean meal during oil extraction:

Unlike regular solvent extraction, this process uses "low-temperature desolventizing" to ensure the production of low-denatured soybean meal. Directly extracting oil after flaking reduces heat treatment, making the protein better for further processing. Low-temperature or flash-desolventized soybean meal has less protein denaturation and a higher water-soluble protein content, making it suitable for products like textured protein, concentrated protein, and isolated protein.

3. Pressed soybean oil: 

This involves cleaning, peeling, crushing, softening, flaking, steaming, and pressing the soybeans to extract oil. While pressed oil retains more nutrients, the oil yield is lower due to soybeans' relatively low oil content (about 20%). Low-temperature pressing and fine filtration produce soybean oil with natural flavor, avoiding harmful residues like acids and heavy metals. However, pressing leaves more residual oil in the meal, making it inefficient for large-scale factories. Thus, they often opt for solvent extraction.

Solvent-extracted soybean oil undergoes refining processes like degumming, neutralizing, decolorizing, deodorizing, and dewaxing to remove impurities and harmful substances, improving safety and quality for edible use. Refined oil can meet national standards, be marketed as edible oil, or blend with other oils to create mixed oils.