Take a look. Look at the transparency, 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.

Second 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.

Three tastes. 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".

Extended data:

The cooking process of gutter oil is doomed to be unsanitary. Once a large number of harmful microorganisms such as bacteria and fungi reach people's intestines, it will cause people's diarrhea, and in severe cases, it will cause people's nausea, vomiting and a series of gastrointestinal diseases.

Waste oil is mixed with a large amount of sewage, garbage and detergent. After being extracted in the open air in underground workshops, bacteria and harmful chemical components cannot be removed at all. It is an indisputable fact that all "gutter oil" will contain lead seriously exceeding the standard, and eating food made of "gutter oil" with excessive lead content will cause severe abdominal cramps, anemia, toxic liver disease and other symptoms.

People's Daily Online-Master Kong admits that cooking waste oil will teach you five tricks to make instant noodles.

People's Network-What are the hazards of waste oil? 5 strokes to identify waste oil