There's an avocado half you want to save to use later, but what can you do it to prevent it from discoloring and turning slimy in the refrigerator?
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avocados
Credit: Johnny Miller

Whether you're serving burritos or dressing up some toast, you can't go wrong with avocados. They're versatile, delicious, and packed with essential nutrients. The catch, however, is that they're notoriously finicky. Once cut or mashed, avocados will turn blackish-brown in the blink of an eye. So, how do you delay discolored avocados—aside from eating them right away? Ahead, learn how to prevent avocados from turning brown so you can have your guac and eat it, too.

Why Do Avocados Turn Brown?

"Avocados turn brown when their flesh comes in contact with oxygen," says Traci Weintraub, chef and founder of Gracefully Fed. A quick science lesson: Avocado flesh contains phenols (a plant compound) and polyphenol oxidase (an enzyme). Enzymes are proteins that trigger chemical reactions. In the case of avocados, and many other fruits, polyphenol oxidase changes the chemical structure of phenols when they're exposed to oxygen. This reaction produces melanin, a brown-black pigment that's also found in humans. As a result, the once-green avocado flesh turns brown.

How to Prevent Avocado Browning

Now, avocados that have browned due to oxygen exposure aren't necessarily inedible—they're usually safe to eat, says Weintruab, though they might taste slightly bitter. The larger issues are that they can look quite unappealing and their texture might also be somewhat soft, which is another unpleasant side effect of oxygen-induced chemical reactions. Since oxygen is the culprit, the trick to delaying the browning process is shield the flesh from oxygen exposure. A common method is tightly covering the flesh with plastic wrap, but if you're looking for a low-waste approach, you'll be glad to know that you can use standard kitchen ingredients. One technique is to squeeze a bit of fresh lemon or lime juice on the cut side of an avocado. The acidity of the juice will hinder the activity of polyphenol oxidase, which pumps the brakes on browning. Another option is to brush the avocado flesh with olive oil, says Weintraub. This creates "an oily barrier between the fruit and air, thus preventing browning," she explains.

Once you've covered the avocado flesh with olive oil or lemon juice, place it in an air-tight container in the refrigerator for added protection, suggests Weintraub. The container will provide another barrier against oxygen, while the cooler temps will further slow down polyphenol oxidase activity. These factors will help your avocado retain its iconic green color. However, keep in mind that cut avocados in general will only last three to four day in the refrigerator, so you'll still want to eat it as soon as possible.

And if you're heard that leaving the pit in an avocado (or guacamole) helps delay browning, we have some bad news: This is not true, unfortunately. That's because the pit doesn't protect the flesh from oxygen exposure. All that being said, you're better off following one of the methods above to prevent avocado browning.

Comments (2)

Martha Stewart Member
May 22, 2022
Thank you very much for promoting a zero waste solution. Plastic wrap is too often used for minutes and then will spend a thousand years in a landfill. Our great grandchildren will thank us for not leaving them our garbage.
Martha Stewart Member
May 22, 2022
Thank you very much for promoting a zero waste solution. Plastic wrap is too often used for minutes and then will spend a thousand years in a landfill. Our great grandchildren will thank us for not leaving them our garbage.