Air is the enemy of the perfect guacamole. When oxygen hits the avocado’s cells, they begin to age or oxidize. This results in the unappealing discoloration that’s associated with day-old guac. Therefore, the key to keeping the creamy dip’s dreamy hue is to reduce oxygen’s access to the food. We tested some of the most popular tricks for storing guacamole to find the one that works the best. Yes, there was only one. Several failed to prevent browning; others managed to ward off some of the oxidization but ruined the flavor of the guacamole. Read on for our best tips on how to keep guacamole from turning brown so it stays fresh and green the next day—or even the day after that.

Method #1: Storing Guacamole With the Avocado Pit

The technique: Pressing the peels flat against the guacamole surface shields the dip from the air. If air can’t reach it, browning can’t occur. The results: Good luck keeping the peels flat. In our tests, the avocado skins curled back to their original shape, which left the guacamole fully exposed.

Method #2: Covering the Guac With Avocado Peels

The technique: Pressing the avocado peels flat against the guacamole surface shields the dip from air. If air can’t reach it, browning can’t occur. The results: Good luck keeping the peels flat. In our tests, the avocado skins curled back to their original shape, which left the guacamole fully exposed.

Method #3: Adding Extra Lime Juice to Guacamole

The technique: The best guacamole has a bit of bite from the tart juices of a lime, but guacamole-preservation legend has it that if you alter your recipe by adding extra lime juice, you’ll also be rewarded with greener guac for a longer period of time. Is this true? The results: Besides dramatically changing the flavor of the dip, the extra lime juice did not appear to slow oxidization at all. It was still brown about half an inch into the dip the next morning. Fail.

Method #4: Press Plastic Wrap Against the Surface of the Guac

The technique: If air is the enemy, plastic wrap could act as a shield from oxygen exposure. For best results, spread the top of the surface flat so the wrap can get the most contact. The results: The plastic seal lets through more air than you might think. It only marginally improved the guac’s performance after a day in the fridge. The majority of the surface was still brown. Still, it was the second-best method we tried. Browning was just a quarter-inch deep. We stirred it into the remaining guac and no one was the wiser.

Method #5: Cover Guacamole With a Layer of Water

The technique: Water sits atop the dense, fatty food, acting as an impermeable shield. It’s unlikely to be absorbed into the guac, but before serving it a second time, gently pour off the water and give it a swift stir. The results: This was the best of the five methods we tried to keep guacamole from turning brown. The guacamole had almost no discoloration. The water did not dilute the flavor or impact the texture of the dip at all. It may seem peculiar, but you should water your guac before you store it.

Why Water Works Best

Our tests showed that almost nothing can completely block the dip from the air. But a half-inch of water creates a boundary on top of the guacamole that air seems unable to penetrate, at least in part. The day after you make it, the guacamole will be as green as when you put it in the fridge. You can use this technique to keep guacamole green for up to two days. Just cover the bowl with plastic wrap when you store it so you don’t accidentally spill the water or set anything else in it.

Can You Eat Brown Guacamole?

Absolutely. Sure, it’s not the most visually appealing option, but browned guacamole isn’t spoiled or bad, as long as it’s no more than three days old. Brown guacamole may have a slightly different texture—it could be mushier than fresh guac—and it may be a bit more bitter than green avocado, but that doesn’t make it inedible. You could also “hide” the brown by stirring it into the remaining green guac. If you can’t stomach the idea of eating browned, mushy guacamole, you can scrape it off and dump it in the trash. The top layer of guacamole will protect the portions underneath from the air, so in a way, it acts like its own guard—if you’re willing to part with any of this precious dip.