Creamy, nutritious, and ideal on toast, salads, guacamole, and even in smoothies, avocados are one of those foods that seem like a tiny luxury. But as soon as you cut it open, the issue begins: It only takes you to blink once, and that lovely green miracle suddenly starts turning brown. It looks old, and many people think it means the avocado has “gone bad.”
Luckily, browning is a natural reaction that can be drastically slowed down with a hack and ordinary household supplies. Basic science applied cleverly in the kitchen.
Why do avocados go brown
When the avocado is opened, its flesh is exposed to the air. Then, the enzyme polyphenol oxidase (PPO) and some plant compounds called phenols are present in that soft, green portion (which are not an issue on their own within the fruit). The browning happens when the pulp of the avocado and the oxygen in the air combine: PPO and the phenols come into contact with oxygen after the avocado is cut. This starts an oxidation process that gradually changes the surface’s color from bright green to brown. Which is similar to what happens to bananas or sliced apples.
The avocado’s nutritional value is not affected by this color change. The fiber, healthy fats, and vitamins are still present. It mostly alters how it looks, however occasionally the surface texture also changes. The fruit is still edible, but it no longer seem as appealing and fresh, which is why this feels like an aesthetic issue.
Therefore, the key for preserving the looks of your avocado if the browning is caused by both air and enzymes is:
- Reduce contact with oxygen
- Slow down the enzyme activity
The red onion trick and other smart tips
When you cut a red onion, also known as a purple onion, sulfur compounds are released. These substances work as organic antioxidants and reducing agents. When chopped red onion and cut avocado are kept in an airtight container, the onion releases vapors that are beneficial in two ways:
- The causing browning PPO enzyme gets blocked by the sulfur vapors from onions.
- The oxidation reaction is slowed down by the small, controlled atmosphere created by the airtight container.
The avocado and onion should be kept in the same container, but the onion shouldn’t have any direct contact with the fruit pulp tough. Otherwise the onion might transfer some of its flavor to the avocado.
Other simple tips to keep your avocado in a nice shape
- Leave the pit in place:The seed works as a solid block. Although it doesn’t completely shield the surface, it covers a portion of it and prevents oxygen from getting there.
- Use acid like lemon juice or vinegar: A traditional method is to squeeze a lemon or add a splash of vinegar. The low pH of these liquids makes them acidic, which helps in the PPO enzyme’s destruction.
- Cover the surface with plastic wrap: Make sure there are no air bubbles trapped between the wrap and the pulp before pressing the cling film directly onto the cut surface. As a result, the avocado is shielded from oxygen by a tight barrier.
- Add red onion in a closed container: As already mentioned, this technique makes use of both limited air from the sealed box and an antioxidant atmosphere (from the onion vapors).
- Always refrigerate: All chemical reactions, including oxidation, are slowed down by cold temperatures. If you want the avocado to look fresh for longer, you have to keep it in the refrigerator.
The objective is the same—less oxygen, slower enzymes, greener avocado—and each of these approaches deals with the same issue from a slightly different perspective.