Taste: If the oil taste contains spicy taste, it is probably edible oil refined from waste oil;

Odor recognition: take a small amount of cooking oil in your palm and rub it back and forth with your palm. If there is an odor, it is likely to be mixed with waste oil;

Refrigerator: put the oil in the refrigerator at 5-8 degrees Celsius. If there is white precipitation, it is likely to be waste oil. Because in the process of processing edible oil from waste oil, the criminal suspect has not solved the technical problem of separating vegetable oil from animal oil;

High-fire: If the oil color changes after being cooked with high-fire and the color becomes thick and black, it means that it is probably gutter oil, because the small particles contained in gutter oil are easy to change color after being burnt.