The Ridiculously Simple Tip To Prevent Guacamole From Turning Brown

While guacamole is easy to make, keeping it fresh and green is where the challenge lies. Unless you plan to eat the whole batch at once, you may have leftovers. Luckily, there are a few techniques to keep it looking and tasting fresh. Before exploring a few techniques that can help preserve that verdant hue, it helps to consider why guacamole turns brown so quickly. Avocado contains an enzyme called polyphenol oxidase, which causes browning when exposed to oxygen. Hacks for preserving guacamole either prevent further exposure to oxygen or fight oxidation.

Perhaps the easiest way comes right out of your tap. You've heard the expression, "It's like oil and water," right? Since avocado is rich in fat, it doesn't easily mix with water without some effort on your part. You can use a thin layer of water, lemon juice, or lime juice to form a protective barrier, limiting how much oxygen gets into your guac.

After putting your guac in a sealable tub, add in the layer of liquid, and cover it with a lid or plastic wrap. When you are ready to serve the leftover guac, simply pour off the excess water or juice and mix in any remaining moisture (this won't change the flavor or the texture very much). Not only does the water or juice help keep oxygen out, but it also helps the avocado resist oxidation.

Another way to slow oxidation in your guacamole is to use antioxidant-rich ingredients like lime juice. When something is exposed to oxygen, it becomes vulnerable to unstable molecules called free radicals. The free radicals don't have their own electrons, so they steal them from other molecules, damaging the cells and genetic material in the process. Antioxidants give the free radical some of its electrons and as a result, reduce the damage to the other molecules. Since the browning of guacamole is caused by oxidation, antioxidants help slow the process.

Citrus fruits, like limes and lemons, are packed with vitamin C, which happens to be an effective antioxidant. Onions are another common guac ingredient that contains sulfur, which also can act as an antioxidant. If you like the taste of lime juice and onions, including them in your guacamole goes a long way toward naturally preserving it. Some people place half of an onion in their leftover guacamole to protect it from turning brown. Tomatoes also contain vitamin C — just not quite as much as lemon and lime juice. Avocados themselves also contain some antioxidants.

Our relationship status with oxygen is "complicated." We need it to live, but it also triggers aging and cell damage. Even though plants have a different relationship to oxygen, cut fruits and vegetables still suffer damage from exposure. Brown guacamole is safe to eat, it just isn't as appealing as fresh, green guacamole. Other hacks used to keep guacamole and avocados from turning brown seek to slow oxidation, though you can't completely avoid it. 

Storing leftover guacamole in a sealed tub and keeping that tub upside down in your refrigerator will keep oxygen from getting in. Keeping your guacamole in the refrigerator also helps since the cold temperatures slow oxidation. Because avocados brown quickly once exposed to air, you may find your best luck using a combination of simple techniques, including keeping it cold, using antioxidant ingredients, and storing leftovers with a thin layer of water on top. Now the real question is, how will you enjoy all that guac?