If you love avocados but can use the entire one, you know the leftover half turns brown. To avoid this and save for a future use, coat the cut side with olive oil cooking spray. Wrap tightly in plastic wrap. This allows the fat in the spray to shield the fruit’s flesh from oxidation which is the cause of discoloration when exposed to air. This will keep your avocado fresh and green, in the refrigerator, for up to 3 days.