Avocados contain an enzyme called polyphenol oxidase, which when in contact with oxygen in the air, causes avocados to turn brown. The best way then, to keep an avocado from turning brown, is to reduce its contact with air as much as possible.

Brush the exposed area with olive or vegetable oil to create a barrier, then seal in an airtight container—it should keep from browning for about a day or so. Trick No. 4: Buddy up with onion. Onions aren’t just a tasty addition to guacamole—they’

What Makes an Avocado Turn Brown? To prevent the browning, it's important to understand what causes it in the first place. Some fruits and vegetables (apples, potatoes, avocados, and more) contain phenolic compounds and enzymes that, when exposed to o