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.