1. Look at the color. Generally, high-grade oil is light in color and low-grade oil is dark in color (except sesame oil). The color depth of oil varies slightly with different varieties. High-grade oil has good transparency and no turbidity. In addition, high-grade oil has no precipitation and suspended matter, and its viscosity is small.

2. Look at transparency. High transparency, less moisture impurities and excellent texture. After standing for 24 hours, high-quality vegetable oil should be clear and transparent, without turbidity, precipitation and suspended matter.

3. Try it. Normal edible oil has no pungent smell. If there is a pungent smell, it may be that chemical oil has been added or the oil refining is not clean and the solvent residue is high.

4. Look at the time. Oils with long storage time or poor storage conditions are prone to rancidity, so consumers had better buy products produced recently.

Regarding the storage of edible oil, in addition to being dry, dark, low-temperature and sealed, Li He, a researcher at the Institute of Nutrition and Food Safety of China Center for Disease Control and Prevention, suggested that oil drums should be covered with black plastic bags, which can strengthen the protection from light, prevent oil from oxidative deterioration and improve its storage quality.