The terms “cold pressed” and “expeller pressed” both describe mechanical methods of oil extraction, using pressure to physically squeeze oil from seeds, nuts, or fruits without chemical solvents. The key difference between these two techniques is temperature. While both processes rely on intense pressure, the level of heat allowed during extraction dictates the final quality, composition, and use of the oil. This control over temperature creates two distinct categories of oil, each affecting flavor, nutritional value, and cost.
How Expeller Pressing Works
Expeller pressing is a mechanical extraction technique that uses a screw-type press to continuously crush and compress the raw material inside a caged barrel cavity. The powerful screw drives exert significant pressure, efficiently forcing the oil out of the starting material.
This intense pressure and resulting friction inherently generate heat within the press, even without external application. This friction-generated heat causes the oil’s temperature to rise significantly, often reaching 140°F to 210°F (60°C to 99°C).
The moderate heat facilitates extraction, allowing expeller pressing to achieve a high yield. This makes it an economically efficient method for high-volume oil production. Many commodity oils extracted this way are subsequently refined, bleached, and deodorized (RBD) to create a neutral, shelf-stable product.
The Specifics of Cold Pressing
Cold pressing is a variation of expeller pressing, distinguished by the active regulation of temperature during the mechanical process. To earn the “cold pressed” designation, the extraction temperature must be carefully controlled and maintained below a certain threshold.
While this standard varies by region, the industry generally holds the limit at or below 122°F (50°C). Achieving these lower temperatures requires specialized equipment and operational adjustments, such as slowing the press speed to minimize friction and prevent excessive heat buildup.
This deliberate moderation means that less oil is extracted from the raw material, resulting in a significantly lower overall yield compared to standard expeller pressing. The focus is placed on preserving the integrity of the oil rather than maximizing the volume extracted.
Impact on Flavor, Nutrients, and Use
The difference in temperature creates a pronounced contrast in the finished product’s nutritional profile, flavor, and application. Lower-heat cold pressing preserves delicate, heat-sensitive compounds like antioxidants and Vitamin E, which are susceptible to degradation. The gentle process ensures the oil retains a higher concentration of its natural bioactive components.
This preservation extends directly to the oil’s flavor and aroma. Cold pressed oils retain the strong, characteristic taste and fragrance of the source material. Conversely, oils produced with the higher temperatures of expeller pressing often have a milder, more neutral flavor because volatile flavor compounds are reduced by the heat.
Due to the lower yield and higher quality, cold pressed oils are typically premium products. They are used as finishing oils for salads or dressings where their distinct flavor can be appreciated. The cost is higher, reflecting the less efficient extraction process.
Expeller pressed oils are more cost-effective and often have a higher smoke point due to the initial heat exposure. They are preferred as high-volume cooking oils suitable for sautéing or frying, offering a quality alternative to chemically extracted oils.