Why do you place a layer of plastic on guacamole before covering?

The correct answer focuses on the prevention of browning, which is a common issue when it comes to guacamole. This browning occurs due to oxidation, a chemical reaction that happens when the avocado flesh is exposed to air. When you place a layer of plastic wrap directly onto the surface of the guacamole, you minimize the exposure to air, effectively slowing down the oxidation process. This helps maintain the vibrant green color and freshness of the guacamole for a longer period.

In contrast, keeping guacamole warm, adding flavor, or enhancing texture does not relate to the need for a layer of plastic wrap. While warmth might be applicable for other foods, it does not apply to guacamole specifically. Adding flavor or enhancing texture are also more about the ingredients and preparation methods rather than how the guacamole is stored to prevent it from changing color.