Pour fresh mushrooms of different grades into 0.03% sodium metabisulfite solution, gently turn up and down, and wash away sediment, impurities, waxy substances and lipids on the surface of mushrooms. Rinse for 2 minutes and then put it into running water for washing. First boil the prepared 0.1% citric acid solution in the pre boiling machine, and then put the rinsed mushrooms. The ratio of water to mushrooms is about 3:2. Continue to boil until it is thoroughly boiled, 8-10 minutes in total, and then quickly cool down.

There is the taste and smell of fresh mushrooms, no peculiar smell, and the organizational forms are as follows: the whole mushroom is slightly elastic, the size is roughly uniform, the shape of the cap is complete, a small number of mushrooms are allowed to have small cracks, small trimming and thin mushrooms, no serious deformity, and the length of the stipe in the same tank is roughly uniform; Sliced, the mushroom is longitudinally cut, the thickness is about 3.5-5mm.