It is a common phenomenon in life that when food is stored improperly and spoiled, it is not possible to throw it away and eat it again after killing the bacteria by boiling or steaming it through and other heating methods. However, spoiled food is not only bacteria so simple, there are various by-products of microbial metabolism, often these products (or called toxins) are more harmful, and difficult to remove. The following enterotoxin and aflatoxin of Staphylococcus aureus as an example to explain why spoiled food should not be heated and eaten again. First, the bacteria “enterotoxin” food are heated at high temperatures, the bacteria are not killed? Why can not eat it? Because heating can kill the bacteria, but not the toxins left in the food. Just out of the pan food is almost no bacteria, but the living environment, including human skin, mouth and nose are distributed in a variety of bacteria. These “contaminated” food (eaten, stirred, prevented for a long time) more or less brought in a variety of microorganisms, in the food multiplied to produce a variety of by-products and then left in the food, including staphylococci multiplied to produce enterotoxins. Staphylococcus, for example, is one of the most common causes of food poisoning because the enterotoxin produced by Staphylococcus is highly heat-resistant and can be boiled for several hours without being destroyed. It is important to note that overnight food does not necessarily have a rancid taste and may not have enterotoxins, but it is always not fresh food, more or less microbial reproduction, it is not clear what other bacterial metabolites will damage health, so try not to eat, long-term is certainly not good, so always stress to eat fresh food. Second, aflatoxin bacteria generally reproduce in leftovers, while the survival ability of stronger fungi can reproduce on the grain and produce toxins harmful to health, in fact, the most notorious is aflatoxin. Aflatoxin is a secondary metabolite produced by Aspergillus flavus (widespread in the living environment), and in 1993 aflatoxin was classified as a Group I carcinogen by the World Health Organization (WHO) Agency for Research on Cancer, which can induce liver cancer. It especially “favors” four types of food: 1, nuts (peanuts, walnuts, melon seeds, pistachios, hazelnuts, pine nuts, etc.) 2, cereals (corn, rice, barley, wheat, beans, etc.) 3, grain and oil products (peanut oil, corn oil, etc.) 4, homemade fermented foods (curd, yellow sauce, etc.) Aflatoxin is also very heat-resistant, heated to 280 ℃ will not be destroyed, not to mention the boiling point of water 100 ℃ can remove it, so once the food is found to have mold must please discard. In short, whether processed or unprocessed food, has produced toxins by heating usually can not be removed, so not fresh, suspected of deterioration is best not to eat again, the most undesirable is the fear of wasting food heat and then eat, fear of waste to do a good job of food storage or calculate the amount. Cooked food as much as possible to do a short time to eat, eat fresh food, if you want to store should be re-sterilized (thoroughly heated) before it is too late to store in a relatively sterile environment for storage; food and grains should be stored in a ventilated and dry environment to prevent mold and mildew.