"What's with the brown paper bags?" It's a common question. The answer is pretty simple, it keeps them fresher for longer.
You see, the brown paper absorbs excess moisture, allowing the mushrooms to breathe, whereas plastic traps moisture causing the mushrooms to absorb it. That is precisely why mushrooms kept in plastic bags in your fridge will go slimy.
Refrigeration is also key. Keep them cold and they won’t get old! At room temperature, mushrooms lose colour and flavour quickly. It is said that for every hour a mushroom is left in room temperature, the shelf life decreases by 8 hours. The same rule applies to packaged mushrooms. If the package is unopened, the mushrooms will store well in the refrigerator. Once the package is opened, place the mushrooms in a paper bag.
Brown paper bags + Refrigeration = tasty and delicious mushrooms for days!