Generally speaking, flour can no longer be eaten after its expiration date. The shelf life is usually determined by the factory according to the best consumption time of flour. If the shelf life is exceeded, not only will the nutritional value and taste be reduced, but the flour will also be prone to mold, insects and other conditions, producing toxic and harmful substances, which will be harmful to the body after consumption. Flour stored for too long may appear color, properties, odor changes, such as mold, lumps, abnormal smell, etc.. Although high-temperature treatment can reduce some of the harmful substances, but generally can not be completely eliminated. Deteriorated flour is prone to breeding Aspergillus, Trichoderma, Aspergillus and other toxic-producing bacteria, even after cooking can cause symptoms of poisoning, such as headache, nausea, vomiting, abdominal pain, diarrhea, cyanosis, etc. Aspergillus produced aflatoxin may also produce liver damage, the condition can even be life-threatening. It is recommended that daily attention to dietary hygiene, most of the food should not be consumed after the preservation period. In addition, the flour preservation environment also has a certain impact on the storage time, if the flour for a long time in a humid, hot environment, more likely to deterioration, insects or even mold, the shelf life may be shortened.