Moldy refers to the deterioration and discoloration of organic matter due to the growth of mold. A common natural phenomenon occurs in food, which contains a certain amount of starch and protein, and more or less contains some water. The growth and development of molds and eggs need water and warm temperature. Moulds and eggs with low water activity value can't absorb water, but when the water activity value increases after being wetted, moulds and eggs will absorb water in food, and then decompose and eat nutrients in food. Wooden furniture, clothes, etc. It is easy to get moldy after being wet for a long time.