Comparison of Extraction Methods: Solvent Extraction vs. Pressing in Edible Oil Production

Two main extraction methods in edible oil production: solvent extraction and pressing. These methods significantly differ in processing techniques, suitable raw materials, and oil yield.

Differences Between Solvent Extraction and Pressing:

Pressing Method: A physical method that extracts oil by applying manual or mechanical force to oilseeds. The process includes cleaning, crushing, rolling, steaming, and pressing steps.

Solvent Extraction Method: Based on chemical extraction principles, utilizing the mutual solubility of oil and solvents (e.g., hexane) to extract oil through spraying and soaking. It is recognized internationally as an advanced production technique.

Differences in Suitable Raw Materials:

Pressing is mainly applicable to high oil content oilseeds such as peanuts, sunflower seeds, and rapeseeds, or oilseeds requiring specific flavors, like peanut oil and sesame oil.

Solvent extraction is ideal for low oil content oilseeds like soybeans and rice bran, and for producing non-flavored oils. This method boasts higher oil yields, lower residual oil in meal, large processing capacity, and high automation.

Differences in Oil Yield:

Pressing method results in higher residual oil in meal, lower oil yield, and higher energy consumption.

Solvent extraction achieves high efficiency and minimal residual oil, reducing the residual oil rate to less than 1%. For instance, corn germ processed by solvent extraction reaches an oil yield of up to 97%, compared to only 65% with the pressing method.

Equipment Required for Solvent Extraction Production Line:

The equipment involved can be categorized into three stages:

Raw Material Pretreatment: This stage cleans, de-stones, crushes, steams, and expands oilseeds based on their type, requiring specific equipment for each step.

Oil Extraction: Solvent extraction equipment ensures sufficient contact between solvent and pretreated oilseeds to extract oil and form miscella. By leveraging the differing boiling points of solvent and oil, it evaporates, strips, condenses, and recycles the solvent while separating crude oil. The solvent extraction system comprises a blank extractor, wet meal desolventizing system, miscella evaporation system, and solvent recovery system.

Crude Oil Refining: Solvent extraction requires refining equipment to address impurities and residual solvent in crude oil, ensuring these residues stay within acceptable ranges.

Optimizing Production Methods:

Depending on production needs, suitable oil extraction methods can be chosen. In some cases, combining pressing and solvent extraction can enhance production efficiency and achieve better economic benefits. Understanding the characteristics and differences of these methods helps optimize production processes.