How to Keep Mushrooms Fresh. Mushrooms have a reputation for spoiling quickly. However, you'll be amazed at how much longer your mushrooms last after taking some simple measures to prevent their decay.
Buy fresh mushrooms at a grocery store. Look for young mushrooms, which are closed as opposed to open and flat. Purchase only the amount of mushrooms that you intend to use before the expiration date. Buy mushrooms displaying the latest expiration date on the package.
Adjust your refrigerator's temperature to between 34 and 40 degrees F. Low temperatures keep mushrooms fresh.
Get a brown paper bag. Paper bags are better for mushroom storage than plastic bags because they do not encourage moisture accumulation. If you must store your mushrooms in a plastic bag, wrap them in a paper towel before inserting them into the bag.
Remove the mushrooms from their store packaging. Store packaging usually contains plastic parts, which contribute to decay.
Place the dry mushrooms into the brown paper bag.
Put the bag of mushrooms in your refrigerator. Place the mushrooms somewhere that is largely undisturbed and away from light.
Take only the mushrooms you intend to use from the brown paper bag and clean them. Never wash mushrooms before storing them. Washing mushrooms before storage encourages mold growth.