Solvent extraction is a highly efficient process for extracting edible oil, and oil is separated from raw materials by using organic solvents. However, the crude oil obtained directly by solvent extraction cannot be eaten directly and must be refined. This is because unrefined crude oil may contain some substances harmful to human health, and its sensory quality and storage performance do not meet the requirements of edible oil.

Firstly, a small amount of organic solvent may remain in the crude oil extracted by solvent extraction. Although modern technology will minimize solvent residue, it still needs to be further removed through refining process to ensure the safety of edible oil.

Secondly, crude oil may also contain some natural impurities, such as phospholipids, free fatty acids, pigments, waxes and odorous substances. These impurities will not only affect the taste and appearance of edible oil, but also shorten its shelf life. For example, high content of free fatty acids will lead to oxidative deterioration of edible oil, while pigments and odor substances will affect the sensory quality of edible oil.

Besides, the refining process can also remove some potentially harmful components, such as heavy metals, pesticide residues and aflatoxins. If these substances are not effectively removed, long-term intake may cause harm to human health.

Refining usually includes degumming, deacidification, decoloration, deodorization and other steps. Through these processes, crude oil can be transformed into pure, transparent and odorless refined oil, which not only meets the food safety standards, but also improves the taste and storage stability.

To sum up, the edible oil extracted by solvent extraction must be refined in order to ensure food safety, improve quality and extend shelf life. When consumers buy edible oil, they should also choose products that have been treated by formal refining process to ensure health and safety.