> What about leftover avocado? Any way to keep it from browning? Oxygen is the enemy of avocados—it's what causes them to turn that unsightly brown.

I am very surprised this article nor the comments mention what my wife does: keep the pit inside the mashed avocado. It will stay green much longer!

No idea where she learned this but it works. We always joke to friends this tricks the avocado into thinking it is still complete.