Guacamole will turn brown quickly if you leave it exposed to air.
Guacamole, like most avocado products, has a tendency to turn brown (or even black) fairly quickly when left uncovered. The avocados in the guacamole react with oxygen, leading to this discoloration. Most guacamole contains lime juice, which contributes to the flavor and also helps delay the discoloration process. This lime juice alone, however, is not enough to keep the guacamole from going brown. With a few simple precautions, you can help keep your guacamole vibrantly green.
Instructions
1. Place the guacamole in an airtight container. Push the guacamole firmly into the container with the back of a spoon, removing any visible or large air bubbles. These bubbles contain oxygen and therefore contribute to discoloration in the guacamole.
2. Sprinkle lime juice over the entire exposed surface of the guacamole. Because the reaction between oxygen and the avocados is what causes the discoloration, you only need to cover the exposed parts of the guacamole with lime juice; you do not need to mix juice into the guacamole. The acid in the juice will help keep the guacamole green.
3. Cover the entire exposed surface of the guacamole with plastic wrap. Pat the wrap down firmly to remove any air bubbles between the plastic and the guacamole. Do not, however, push down on the wrap so hard that you squeeze the lime juice off the surface of the guacamole.
4. Seal your airtight container to prevent more air (and therefore oxygen) from entering. You can store the guacamole at room temperature for several hours before serving it or in the refrigerator for up to a week.
Tags: lime juice, surface guacamole, airtight container, entire exposed, entire exposed surface, exposed surface, exposed surface guacamole