Why edible oil need refined?

The purpose of oil refining, usually referred to as oil purification, is to process crude oil. The presence of impurities in crude oil not only affects the edible value and safe storage of the oil but also creates difficulties in further processing. However, the goal of refining is not to remove all impurities from the oil, but rather to eliminate harmful and undesirable impurities, such as gossypol, protein, phospholipids, mucilage, water, etc., which can be detrimental to consumption, storage, and industrial production. Beneficial "impurities," such as tocopherols, are retained. Therefore, depending on different requirements and uses, unwanted and harmful impurities are removed from the oil to obtain finished oil that meets specific quality standards, and this is the purpose of oil refining.

Crude oil generally refers to the oil extracted from oilseeds during the extraction or pressing process, which contains certain impurities unsuitable for consumption (or industrial use). The main component of crude oil is a mixture of triglycerides (commonly known as neutral oil). In addition to neutral oil, crude oil also contains non-glyceride substances (collectively known as impurities), which can be roughly categorized into three classes: mechanical impurities, liposoluble impurities, and water-soluble impurities.