Because pineapples don't ripen once they're picked, they arrive at your grocery store ready to eat -- giving you only a short time before they start to turn brown. The most effective way to keep a pineapple from turning brown is to to properly store and then quickly enjoy eating the fruit.
Buy the freshest-looking pineapple at the store -- look for fresh, green leaves with no drying or yellowing at the tips, as well as firm skin without soft or dark spots.
The cold temperature in your refrigerator slows down the enzymes in pineapple that cause it to age and turn brown, so refrigerate the whole fruit immediately. According to the Still Tasty website, a whole pineapple stays fresh -- with yellow flesh -- at room temperature for only one to two days, but stays fresh and bright for three to five days in the refrigerator.
Even if you don't plan to eat the pineapple the day you bring it home, you'll keep it from turning brown if you cut it before putting it into the refrigerator. This makes it more accessible so it's easier to eat before it goes bad. Wrapped in plastic, cut pineapple stays yellow for three to four days in the fridge.
Skin the pineapple and cut it into bite-size chunks or wedges; large wedges expose less surface of the cut pineapple to air than chunks do, reducing the amount of oxidation and browning.
Any acidic substance inhibits some browning, or oxidation, in pineapples by killing some enzymes that react with oxygen to turn the fruit brown. Add the liquid or powder to cut pineapple and stir the fruit thoroughly so all its surfaces are covered. Options include:
- Fresh lemon juice, which gives you an easily available and multipurpose acidic liquid that adds a bit of citrus flavor to the pineapple as well as preventing some browning. Simply squeeze the juice over cut pineapple before wrapping it and storing it in the fridge.
- Vinegar -- like lemon juice it's readily available, multipurpose and highly acidic. Use it as you would lemon juice, and rinse it off the pineapple right before you're ready to eat it.
- Ascorbic acid powder, sold either as vitamin C or as ascorbic acid, which prevents browning when you sprinkle it onto pineapple.
Store cut pineapple in the freezer if you want to stop all ripening and prevent any browning. Cut pineapple stays good in the freezer, wrapped in freezer-safe plastic or any airtight container for 10 to 12 months.