Taking the production of dim sum as an example, the central kitchen's dim sum is processed in huge quantities, the steamer is steamed in multiple cages at a time, and the cages are stacked on top of each other in a high number of layers. The steam flow is concentrated in the center of the steamer and goes upwards, then downwards from the center of the steamer when it touches the lid of the cage. Therefore, at the beginning of a period of time the temperature inside the steamer is not uniform. There is a temperature time difference between the center of the steamer, the periphery of the upper steamer, the periphery of the middle and lower steamer, etc. This can easily lead to a situation where when the center of the steamer has already started to steam, the steamer edges of the steamer will continue to ferment, therefore, the focus of the process is on the control of the fermentation and steam cooking process. For large scale production, one scrap per cage means more than 5/1000 of scrap rate, which is absolutely unacceptable for cost control, but for technology, it is hard to avoid a little bit improper operation in the production process.