1. Looking at the transparency, the pure vegetable oil is transparent, and the transparency will decrease due to the mixing of alkali grease, wax and impurities in the production process; Look at the color, pure oil is colorless, and the oil will be colored because the pigment in the oil is dissolved in the oil in the production process; Look at the sediment, its main component is impurities. 2. The freezing point of pure oil is 1 degrees Celsius, while the freezing point of inferior oil (such as gutter oil) is 8 degrees Celsius, so you can put some on the table with chopsticks while eating vegetables to see if it will solidify quickly. If so, it proves that the oil quality is not very pure.

smell: each oil has its own unique smell. You can drop a drop or two of oil on your palm, rub your hands together, and smell it carefully when you are hot. Oil with odor indicates that there is a problem with the quality, and it is likely to be waste oil with odor; If there is a smell of mineral oil, you can't buy it. Taste: Take a drop of oil with chopsticks and taste it carefully. The oil with sour taste is unqualified, the oil with bitter taste has been rancid, and the oil with peculiar smell may be "waste oil".

Listen: Take a drop or two of oil from the bottom of the oil layer, apply it on flammable paper, light it and listen to its sound. The products with normal combustion and no noise are qualified products; If the combustion is abnormal and makes a "squeaky" sound, the water content exceeds the standard and it is an unqualified product; When burning, it makes a "crackling" explosion, indicating that the water content of the oil is seriously exceeding the standard, and it may be an adulterated product, so it is absolutely impossible to buy it.

q: ask the merchant about the purchase channel, and ask for the purchase invoice or check the sampling inspection report of the local food hygiene supervision department if necessary.