Storing mushrooms is a bit tricky because the refrigerator is not an ideal place for mushrooms because Mushrooms like humidity while the refrigerator doesn’t provide enough humidity by default. So you have to set up the proper environment if you want to be able to store your mushrooms for more than a few days.
First thing you have to do is remove the Mushrooms from the original package and place them in a clean container that gives them room to breath… they can’t be packed together tightly. Next, wrap it tightly with a layer of saran wrap, then use a tooth pick and poke holes all over the top.
Next, you want to take a paper towel and fold it into half, then half again in the other direction (fold it into a 1/4 of the original size). Get the paper towel wet so it is damp, but not dripping wet. Place the paper towel on top of the first layer of saran wrap, then cover it with another layer of saran wrap (tightly).
Finally, use the tooth pick to poke holes into the top saran wrap but only poke holes on top of where the damp paper towel is. Do not poke holes that go through both layers of saran wrap. What you are doing is creating a humidity barrier so the air has to pass through the wet paper towel to get in and out of the container.
Normally when I store mushrooms without using this method of storage the mushrooms only last 3 – 4 days max before they start to either dry out or they get mushy, depending on if I open original package seal or keep it unopened. Using this method I’ve been able to store mushrooms for over a week and they are still fresh. you can technically get the same result by putting the mushrooms into a large bowl and placing a damp wash cloth on top, but I don’t like doing that because you have to re-dampen the towel every day. I like this method because it takes me 2 minutes to do it and I don’t have to touch it again for a week.