Soybean oil is made through two primary methods: mechanical pressing and solvent extraction.
1. Mechanical Pressing
Mechanical pressing, also known as expeller pressing or cold pressing, involves physically squeezing the oil out of the soybeans. Here's the process:
- Soybean Preparation: Soybeans are cleaned and potentially heated slightly to improve oil yield.
- Pressing: The soybeans are fed into a mechanical press, which applies high pressure to crush the beans.
- Oil Extraction: This pressure forces the oil out of the soybeans.
- Filtration: The extracted oil is then filtered to remove any solid particles or impurities.
Oils produced through mechanical pressing are often marketed as "cold-pressed" or "expeller-pressed" and may have a slightly different flavor profile compared to solvent-extracted oils.
2. Solvent Extraction
Solvent extraction is a more efficient method for extracting oil from soybeans, yielding a higher percentage of oil. Here's how it works:
- Soybean Preparation: Soybeans are cleaned, cracked, dehulled, and rolled into flakes to increase the surface area for solvent contact.
- Solvent Application: The soybean flakes are then mixed with a solvent, typically hexane.
- Oil Dissolution: The hexane dissolves the oil from the soybean flakes.
- Separation: The solvent-oil mixture (miscella) is separated from the soybean flakes. The remaining flakes, now mostly oil-free, are processed into soybean meal for animal feed.
- Solvent Removal: The hexane is then evaporated from the miscella, leaving behind the crude soybean oil. The hexane is recovered and reused.
- Refining: The crude soybean oil is refined to remove impurities, such as gums, free fatty acids, and pigments, resulting in a bland, light-colored oil. The refining process may involve degumming, neutralization, bleaching, and deodorization.
In summary, soybean oil production involves either mechanically pressing the oil out of soybeans or using a solvent like hexane to dissolve the oil, followed by solvent removal and refining.
