Edible oil is divided into two categories: animal oil and vegetable oil, and now there are many different kinds of edible oil. However, almost every family has had the experience of oil becoming “haram” and producing an unpleasant smell, which is caused by long-term storage or improper storage, oil rancidity. Oil is composed of one molecule of glycerol and three molecules of fatty acids. The cause of oil rancidity, one is due to the oil contained in the raw material residue by the microbial enzymes generated by the decomposition caused; two is due to edible oil in the sun, high temperature or trace metal under the action of hydrolysis and caused. After the decomposition of oil and grease, free out many unsaturated fatty acids, such unsaturated fatty acids are easily oxidized, resulting in aldehydes, ketones and other oxides, which is the source of the “harsh” taste. After the oil becomes “haram”, not only the vitamins contained are reduced, its nutritional value is also reduced. If you eat highly sour and degraded “harsh” cooking oil, it can also cause food poisoning, which is characterized by stomach discomfort, nausea, dizziness, joint and muscle pain, etc. Soon after eating, some patients have increased body temperature. If there are serious gastrointestinal symptoms or other manifestations, go to the hospital promptly. Poisoning Prevention: Sealing and protection from light can increase the shelf life of edible oils. When storing cooking oil (especially in summer), adding 200-300mg of vitamin E per kilogram of oil can delay deterioration. Do not consume edible oil that has become tasteless.