Soybean oil is primarily extracted through a process involving solvent washing of soybean flakes using hexane.
The modern method for extracting oil from soybeans is largely based on solvent extraction. This technique is highly efficient for maximizing oil yield. At contemporary processing plants, oil is extracted from soybeans by solvent washing of soybean flakes which have been preconditioned for optimal separation of oil from the soybean meal, using hexane as solvent. The core piece of equipment facilitating this process is the solvent extractor.
The Soybean Oil Extraction Process
Extracting oil from soybeans involves several key steps to prepare the beans and then separate the oil using a chemical solvent.
Key Steps in Solvent Extraction
- Soybean Preparation: Raw soybeans are cleaned, dried, and cracked into smaller pieces.
- Flaking: The cracked beans are heated slightly and rolled into thin flakes. This increases the surface area, making it easier for the solvent to penetrate and extract the oil. The reference notes these are soybean flakes which have been preconditioned for optimal separation.
- Solvent Extraction: The preconditioned soybean flakes are introduced into an extractor. Here, they are washed with a solvent, most commonly hexane. As stated in the reference, using hexane as solvent is standard. The solvent dissolves the oil from the flakes, creating a mixture of oil and solvent (called "miscella") and leaving behind the solid soybean meal. The heart of the solvent extraction plant for vegetable oil is the solvent extractor.
- Solvent Removal: The miscella (oil + solvent) is heated to evaporate the hexane. The hexane vapor is then condensed and recycled for future use. The extracted soybean meal also retains some solvent, which is removed through heating and steaming.
- Oil Refining: The crude soybean oil obtained after solvent removal typically undergoes refining steps like degumming, neutralizing, bleaching, and deodorizing to remove impurities and improve its quality, color, and stability for various uses (like cooking oils or ingredients).
| Step | Purpose | Medium/Equipment |
|---|---|---|
| Preparation | Clean and size beans | Cleaners, Dryers, Crackers |
| Flaking | Increase surface area | Rollers |
| Solvent Extraction | Dissolve oil from flakes | Solvent Extractor (using hexane) |
| Solvent Removal | Separate oil from solvent | Evaporators, Strippers |
| Refining | Purify and improve oil quality | Various refining equipment (degumming, bleaching) |
Why Solvent Extraction with Hexane?
Solvent extraction, particularly using hexane, is widely adopted in the industry because:
- It is highly efficient at extracting nearly all the oil content from the soybeans, leading to a higher yield compared to mechanical pressing alone.
- Hexane is effective at dissolving triglycerides (the main component of vegetable oils).
- It is relatively easy to recover and recycle the solvent from both the oil and the meal.
In summary, extracting soybean oil in modern facilities primarily relies on washing preconditioned soybean flakes with hexane in a solvent extractor to separate the oil from the solid material.
