Solution: Keep them in a paper bag, not plastic.Mushrooms are a delicious, hearty ingredient to use in everything from a chopped salad and a morning omelet to a stir-fry, but nothing is more unappetizing than reaching in for the vegetable and pulling out a slimy, mushy mess.Keeping mushrooms meaty and fresh for as long as possible is all about how you store them. When we get veggies home, many of us reach for plastic bags, but for mushrooms, paper should be your go-to. Plastic traps in moisture, which causes mushrooms to mildew; opting for paper allows the vegetable to breathe and for moisture to escape, slowing the rate at which they begin to decay, says Nasar.No paper bags on hand? You can still keep mushrooms from spoiling by keeping them in their original packaging, says Nasar, but cover with plastic wrap that has holes poked in it for better air circulation.