Mushrooms can sometimes bought in bulk at the supermarket when they are sold by the pound. However, more often, fresh mushrooms are packaged in 8-ounce plastic containers which are wrapped in plastic wrap. Is is OK to leave them in this container?
While the mushrooms you purchase in a plastic tub, usually common white or bella mushrooms will probably be fine when you buy them, this is actually the worse possible way that mushrooms can be stored. If you leave the mushrooms wrapped up in plastic, they will quickly develop brown spots and slimy appearance and feel. They may also appear pitted. Certainly, if the mushrooms already look like this in the grocery store, you shouldn’t buy them. They have been in their sealed container too long. Although you may not be able to tell, they may have started to develop a bad, somewhat fishy, odor.
Ideally, you should purchase your mushrooms from the bulk bin. This way, you can be more assured that every mushroom meets your quality standards. Although mushrooms stored in the open air will dry out, you can easily tell by checking the edges, which will dry out first. You will probably place the mushrooms in a plastic bag, of course, when purchasing them. Do not tie the bag shut. Give the top a loose twist — just enough to keep the mushrooms from spilling out.
How to Store Mushrooms
If you must purchase mushrooms in plastic wrapped tubs, do NOT store them in these containers, or in a plastic produce bag. As soon as you get your mushrooms home, unwrap them and place them either in an open bowl or inside a paper bag in the refrigerator. Mushrooms stored in a bowl will inside the fridge will do fine for a couple of days. A paper bag may allow you to keep them for an additional day or two. Some folks like to layer paper towels inside the bag to help absorb any excess moisture. Place on paper towel at the bottom of the bag, and place a layer of mushrooms on top of it, then layer another towel, and another layer of mushrooms, etc., until all the mushrooms are layered in the bag.
Mushrooms are Mostly Water
While the average vegetable may be around 70% water, mushrooms contain 90% water. Also unlike vegetables, they have no protective skin. This means that water can easily evaporate out of the mushrooms. If they are open to the air, this will cause them to dry out. But if they are sealed in a plastic tub or a plastic bag, water droplets will collect on the inside of the container. This will raise the humidity inside the enclosure and this high humidity will cause the mushrooms to go bad much more quickly. One of the first signs is a brown or black splotchy appearance. Poking holes in the plastic won’t help. Mushrooms must be stored in a breathable container. A simple paper bag is a great option, then, although cloth bag products exist.