3 Ways to Keep an Avocado Fresh and Prevent It from Turning Brown

Place the avocado in an airtight container with about a quarter cup of freshly chopped red onion. The sulfur compounds in the onion (you know, the ones that make you cry) will oxidize on the green surface and prevent it from browning…for a couple of days at least.

Right before you seal the un-eaten avocado half in an airtight container, use a pastry brush (or paper towel, in a pinch) to slather the green surface with olive oil. Then pop it in the fridge.

Same deal as olive oil. Brush the juice onto the exposed green. Then, instead of using an airtight container, wrap the avocado half in Saran wrap. Just be sure you press the plastic against the surface to help seal in the lemon juice.