Why Do Avocados Turn Brown?

by Charlie
Avocados

Avocados are a modern kitchen staple. The “healthy fat” is perfect spread on toast, blended into smoothies, or diced onto salads. And who can forget guacamole, where the avocado is the star of the show. 

The creamy green goodness is that is avocado is a fruit, not a vegetable. Yep, the avocado is considered a big berry with one single seed. And not to mention that cutting into an avocado is always exciting; you never know if you will get a tiny seed or a large one.

An avocado is versatile, delicious, and gorgeously green. Until it turns brown, that is.

So, why do avocados turn brown? Avocados turn brown because they contain enzymes called polyphenol oxidase. When you expose the flesh of an avocado to oxygen, the enzymes begin to oxidize, rapidly turning that vibrant green color into an unappealing shade of brown. 

In more scientific terms, the polyphenol oxidase helps convert the phenolic compounds found in an avocado to another class of compounds, which are called quinones. Quinones polymerize, meaning they join together smaller particles into a long chain, resulting in polyphenols. Guess what color shows up when this occurs? Yep, it’s brown. 

But wait – an avocado’s flesh turns brown not only because of oxygen exposure but also because the plant cells become damaged when you cut into the fruit.

So, it’s quite simple – it’s just science doing its thing. But how frustrating is it to wait until your avocado is the perfect ripeness, use half of it in your morning smoothie, and then have the other half turn brown before the day is done?

Before we get any further, let’s break down the avocado itself.

What is an Avocado, Exactly?

We’ve established that an avocado is a fruit, but there is much more to discover.

For example, did you know that there are three botanical races of avocados? There’s the Mexican avocado, Guatemalan avocado, and West Indian avocado. There are also hybrid versions. 

Avocados come in various shapes and sizes, but all versions of the fruit have a similar makeup.

  • Exocarp: Frequently referred to as the skin, the exocarp can be thick, thin, light green or dark, almost-black green. It all depends on the type of avocado.
  • Mesocarp: The mesocarp is a fancy name for the flesh of the avocado. It’s the creamy, green insides of the avocado. The flesh contains very little sugar or starch. It’s mainly composed of fatty acids, such as linoleic acid and oleic acid.
  • Endocarp: You may have noticed a thin layer of film between the flesh of the avocado and its seed. Or maybe not, as it’s not really that noticeable. Either way, this is the endocarp.
  • Seed: Avocados contain a seed in the middle, which can vary in size depending on the type of avocado. 

Now, you probably think that you can impress all of your friends with your extensive avocado knowledge, but there’s more. Like, can you prevent an avocado from turning brown? If so, how? Read on to find out more.

How Can You Keep an Avocado from Turning Brown?

It’s always frustrating when you buy a bounty of fruit and vegetables just to have them go bad before you can eat them. Avocados will turn brown in a blink of an eye. Yes, really that fast (almost). So, how can you keep an avocado from changing from green to brown?

There are several ways to keep an avocado from turning brown, such as limiting oxygen exposure, keeping the fruit in the refrigerator, or pairing it with anti-browning fruits and veggies. 

Limit an Avocado’s Oxygen Exposure 

There are several methods of limiting oxygen exposure when storing avocados. You can’t simply throw half of an avocado in the fridge and expect it to stay green – oh no. You need to cover it tightly with cling-wrap immediately after use. That will help prolong the life of that gorgeous green.  

Pair an Avocado with Certain Fruits and Veggies

You may use lemon juice to keep your apple slices fresh. Well, you can do the same with avocados (an apple browns due to the same enzymatic reactions that occur in an avocado). Just pour a small amount of the acidic juice over the flesh of the avocado and prevent browning from occurring as quickly as it would otherwise.

Are you using onion in your guacamole? Perfect, because you can store your leftover onion with your leftover avocado to prevent browning. Just throw them in an airtight container, and the sulfur-producing onion will keep the enzymes in the avocado from doing their thing (making it go brown, of course.)

Keep Ripe or Cut Avocados Refrigerated

The refrigerator’s cold air slows down the enzymatic reaction in an avocado, so it will stay fresh longer. However, it’s best to keep using one of the other techniques described in this article before putting your avocado in the fridge. For example, add lemon juice or wrap it up tightly.

Bonus tip: Did you bring home hard, unripe avocados from the grocery store? Leave them out on your counter until they have ripened to your liking, and then put them in the fridge. Then you have a perfectly ripe avocado for days rather than hours.

FAQs about Browning Avocados:

Q: How long does it take an avocado to ripen?

A: It typically takes an unripe avocado 3-7 days to ripen. You can place your unripe avocados in a brown paper bag to speed up the process. Then you are only looking at 2-3 days to reach ideal ripeness.

Q: Why does the flesh under the seed of an avocado stay green while the rest of it turns brown?

A: The seed prevents any oxygen from getting to the flesh that is underneath it, so it will not have the same enzymatic reaction that the rest of the avocado has.

Q: How should I store my avocados?

A: In order to ensure that your avocados taste great and last as long as possible, it’s important to understand how to store them. 

  • Unripe avocado: let any unripe avocados sit out on your counter or shelf for 3-7 days (or 2-3 days in a brown paper bag) until they are ripe.
  • Whole, ripe avocado: Once your avocado is ripe, you can put the whole ripe avocado in the fridge so that they keep the consistency you like for longer. 
  • A portion of an avocado: Once you’ve cut into an avocado, the enzymatic process begins immediately. So, if you don’t devour the whole avocado right away, then you can wrap it up, sprinkle it with lemon juice, or pair it with an onion and stick it in the fridge. 

Q: Is it ok to eat an avocado with brown flesh?

A: It is safe to eat an avocado that has turned brown. Of course, if it’s mushy, moldy, or just too gross to consume, throw it out. But a little bit of brown will not make you sick and should still be pretty tasty however you decide to slice, dice, or mash it up!

Final Thoughts

The polyphenol oxidase enzymes found in avocados are the reason why avocados quickly turn from green to brown. However, there are plenty of ways to make sure that your avocado stays in perfectly ripe condition for days (rather than hours). Spread it, mash it, slice it, or dice it – just don’t let it go to waste!

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