2 genius ways to keep avocados from browning
These two tricks will keep your cut avocado fresh for at least a few days:
Squeeze lime or lemon juice over your avocado
Citric acid, a strong antioxidant found in limes and lemons, will slow down the browning process of your avocado. It's also a good reason to put a squeeze of lime juice in your guacamole to keep it fresher for longer.
Pro tip: keep the pit in for even more freshness.
Store chopped red onion with the avocado in an airtight container
The gasses released from a cut red onion prevent oxidation (it's the same gas that makes you tear up when you're cutting the onion).
Make sure the onion only touches the skin of the avocado to make sure there's no onion-y flavor in your avocado.