Here’s a tip to help keep your “guac” green. Once you cut into an avocado, discoloration occurs almost immediately, but adding an acid like lemon or lime juice helps reduce discoloration and gives you an added boost of flavor.
You’ve probably noticed, however, that when you store your guacamole it develops a dark layer on top. Instead of just scraping it off and throwing it away, try this. Take a small piece of plastic wrap, just slightly larger than the inside of the bowl you’re storing your guacamole in. Rub one side of the wrap with fresh lemon, squeezing slightly to release a film of juice, and place it juice side down gently but firmly right on top of the guacomole. With a blunt knife, tuck a tiny amount of the wrap down between the bowl and the dip creating a plastic “skin” on top of the mixture. The goal is to seal out air.
Ideally you’ll want to prepare guacamole and eat it right away, but when you have leftovers, this storage method will help keep the guacamole looking nice and green up to 2 days. In general, avocados should be consumed quickly when they’re at their peak of flavor and ripeness.