Soybean oil, commonly known as soybean salad oil, is one of the most frequently used cooking oils. Soybean oil is extracted from soybeans by pressing or through leaching and refining processes. Cold-pressed soybean oil has a lighter color and a milder flavor of raw soybeans. Hot-pressed soybean oil, due to the high-temperature treatment of raw materials, has a high oil yield, but its color is darker and it has a stronger smell of raw soybeans. According to different processing procedures, it can be further classified into crude soybean oil, filtered soybean oil and refined soybean oil. Crude soybean oil is yellowish-brown in color, while most refined ones are light yellow and have a relatively high viscosity. After being left in the air for a long time, an unstable film will form on the surface of soybean oil. Soybean oil is more nutritious than other oils and fats and is favored by people in all regions of our country. The oil refined from soybeans is mainly used for salads, cooking or making vegetable cream.