Soft and elastic, the size in the same pot is roughly uniform, without umbrella opening mushroom, deformed mushroom, desmoped mushroom, spotted mushroom, pest infested mushroom, oxidized mushroom, hollow mushroom and thin skin mushroom not more than 10% whole mushroom, button mushroom: the diameter of the fungus is not more than 40 mm, the shape of the cap is complete, the section of the stipe is flat, the length of the whole mushroom stipe is not more than 8 mm, the length of the stipe is basically the same, and the stipe of button mushroom is flush with the cap.

Grading shall be carried out according to the specification requirements of processing cans, and the mushroom bodies that are not suitable for full packaging, such as cracked cap, deformed cap, open umbrella and uneven color, shall be picked out, and the diameter of about 1.5cm is the first grade mushroom; The diameter of about 2.5cm is the second grade mushroom; The diameter of about 3.5cm is the third grade mushroom; Those below 4.5cm can be used for processing sliced mushrooms, and those with a diameter of more than 4.5cm can be used for processing shredded mushrooms. The tinned iron cans or glass bottles shall be strictly inspected before being filled, and the unqualified empty cans shall be removed. Then wash it in hot water at 90-95 ℃, put it upside down on a clean shelf and drain it for standby.

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.

After harvesting the mushrooms, remove the stalks with mud roots and immediately immerse them in clean water or 0.6% salt water. Mechanical injury shall be strictly prevented during picking and transportation; If it cannot be quickly transported back to the factory for processing within 3h after harvest, it must be soaked with 0.6% brine; Or use 0.03% sodium pyrosulfite solution to wash, soak and transport to prevent mushrooms from emerging. If the mushroom is soaked in 0.1% sodium pyrosulfite solution for 5-10 min in the production area, picked up and packed in a film bag, packed in a box, and transported back to the factory, it can be put into production only after 30 min of rinsing.