2, mushrooms are drowned in order to remove the melanin of straw mushrooms. If mushrooms are fresh, they don't need to be blanched. But generally speaking, it takes at least 6 hours from picking to buying home. Because of its special biological characteristics, the mycelium of Volvariella volvacea will autolyse in the environment below 20 degrees, so the fruiting body will have bitter taste and earthy smell. Therefore, blanching can effectively remove these odors.