Aside from pesky fruit flies, bananas with brown spots are still totally usable. But exactly how brown is too brown, even for banana bread? Read on to find out the limits of brown bananas, how to use them and, most importantly, when not to use them.

Bananas are one of the most delicious and versatile fruits out there. They're most often enjoyed as is for breakfast or as a snack, and they can be cooked—be it baked, caramelized or flambéed—when ripe or even overripe. But exactly when does a brown, overripe banana become unusable? Here's everything you need to know, from when you should toss a really brown banana to how to pick the perfect one for your needs.

Is It safe to eat brown bananas?

It all really depends on just how brown your banana is. Ultimately, as long as your banana is not moldy, and is not slimy or overly soft and squishy when you remove the peel, it is safe to eat brown bananas.

A banana with brown spots or freckles is fine. These spots are one indicator of ripeness (smell is another indicator—more on a banana's fragrance in a minute). Spots will be various shades of brown, and will show up as speckling over the peel.

Black areas or large sections of dark brown on a banana are more likely to be bruises, caused by either the natural ripening process or exposure to air. Bananas are a high-ethylene-gas-emitting fruit, just like apples, avocados, stone fruits, pears and tomatoes, among others. (Learn why you should keep these fruits separate from low-ethylene-gas-emitting fruits and how to store them here.) The emission of ethylene is natural and part of the banana's ripening process, including over-ripening, the stage at which we may notice bruising. These bruises may easily be cut away from the fruit.

two brown bananas on a yellow background
Credit: Getty Images / Massimo Ravera

When the flesh of a banana is exposed to air due to a tear or hole in the peel, oxidation (aka enzymatic browning) occurs, which also appears as bruising. According to an article by Svenja Lohner in Scientific American, "The enzyme responsible for the browning is called polyphenol oxidase (or PPO). In the presence of oxygen the PPO enzyme changes substances known as phenolic compounds (through a process of oxidation) into different compounds called quinones. The quinones then react with other compounds to form melanin. Melanin is the same dark brown pigment that colors hair, skin and the irises of our eyes. It also turns fruit and vegetables brown."

So, oxidized bananas, while they may be less eye-catching than when they're in their sunny, yellow form, are perfectly fine to eat. (Bananas with skin that is mostly brown, like what you see in the above picture, are actually ideal for baking—more on that later!)

When is a banana too brown?

Trust your gut—literally. If the banana is totally brown with no yellow showing, is soft or squishy, is showing signs of mold, is leaking fluid or smells rotten, it is beyond saving.

A banana that is ripe will have a yellow skin covered in brown spots, will smell sweetly of banana and will be the texture of a ripe avocado. An overripe banana that is not fit for consumption raw or cooked will be totally brown or have black bruises and will smell fermented or like alcohol or will have an undertone of garbage. Overripe bananas will often seep fluid.

What makes bananas rot?

Usually, exposure of the banana's flesh to air is the primary culprit in rotting. Any opening in the protective coating of the peel allows oxygen to get to the flesh, which can cause the flesh to first oxidize and then to break down. Damaged peels can also give access to pests like fruit flies or house flies. 

Skip bananas with obvious bruising or soft spots. And always buy bananas with their stems still attached. Any opening in the peel allows air and bacteria to enter the fruit, which means it'll go bad quicker.

Can I cook with brown bananas?

For baking, you always want to use brown bananas. Brown bananas have a more intense flavor, which will come through even after cooking. That's because brown bananas have gone far enough through the ripening stage that their starches have converted to sugar, which intensifies the flavor and prevents any gummy or starchy texture negatively impacting your baked goods.

If you have ever had banana bread or a muffin that was rubbery, or that barely tasted like banana, chances are the bananas were not ripe enough. Nutritionally, there is no significant difference between the healthful benefits of bananas in the various stages of ripening—they're all good for you! (Learn what this dietitian has to say about the health benefits of bananas.)

The fragrance of bananas also increases as they ripen and release aromatic esters, particularly isoamyl acetate. According to the American Chemical Society, "Isoamyl acetate is naturally produced by ripening fruit. It creates a strong, fruity banana or pear odor that is widely used to flavor foods, attract bees, and improve the smell of everything from perfumes to shoe polish."

How to pick the perfect banana

Choosing a perfect banana depends on when you want to eat it and how you intend to use it. For a more savory dish, you may want bananas that are underripe, more green than yellow. These bananas will be harder, more like a carrot.

If you are looking for a peel-and-go snack, or want to slice it over your cereal, reach for a banana that's bright yellow with minimal brown spots. Preference also comes into play here. Some people prefer bananas that are just barely ripe, when the flesh is still relatively firm and the flavor is not too sweet or fragrant. Some prefer a fully ripe banana, which will be softer and have a more intense banana flavor. Fully ripe bananas will be yellow with brown spotting like freckles.

For baking, when you want the banana flavor to shine through, wait until your bananas are entirely covered with brown spots and smell very fragrant. If your bananas have ripened to the perfect stage for baking, but you're not ready to make banana bread just yet, freeze them!

Bottom line

Bananas will always be a great fruit to have on hand, whether you need a nutritious snack on the go, or are looking to create decadent desserts. And if you choose the right ones, you can get a good long edible life out of them. Even the brown ones.