Why Do Bananas Turn Black So Quickly? – Unpeeling the Truth

10 September, 2024

Why Do Bananas Turn Black?

Why do bananas turn black?

According to scientists, bananas and other fruits react to the hormone ethylene in the air, which causes the acids in the bananas to break down, making them softer and sweeter. Simultaneously, the chlorophyll in the bananas is broken down, and over time, the bananas turn yellow as they ripen.

However, while other fruits only react to small amounts of ethylene, bananas continue to react to this hormone, causing their yellow pigments to gradually turn brown or develop dark brown spots.

Peeling a banana increases its exposure to ethylene, accelerating the ripening process and making it more prone to turning black.

For other fruits, refrigeration helps maintain freshness, but why do bananas still turn black quickly when stored in the fridge?

At low temperatures, the molecular membrane in the banana peel breaks down, releasing enzymes that oxidize the phenolic compounds in the peel, eventually turning it black.

Is it safe to eat bananas that have turned black?

Typically, you would only eat bananas when they are just ripe and quickly discard those showing signs of blackening.

In reality, while overly ripe bananas with spots or streaks may lose some of their nutritional value, they still contain high levels of beneficial antioxidants.

Therefore, even if they have started to turn black or have spots, they are still safe to consume and can be used in various ways, such as making banana bread, adding them to smoothies, or turning them into banana jam, although the flavor may not be as appealing as a fresh banana.

Frequently asked questions

Bananas turn black due to a process called enzymatic browning. This occurs when an enzyme called polyphenol oxidase (PPO) reacts with oxygen and compounds in the banana’s flesh, resulting in the production of melanin – the same pigment that gives human skin its color. This reaction is accelerated by damage to the fruit’s cells, such as bruising or cutting, and is also influenced by the ripeness of the banana and storage conditions.

To slow down the browning process, you can try a few methods: first, store bananas away from direct sunlight and at a cool room temperature. Second, wrap the stem of the banana bunch with plastic wrap, as the gas ethylene emitted from the stems speeds up ripening and browning. Finally, separate individual bananas and coat the cut ends with lemon juice or vinegar, which are acidic and inhibit the enzyme’s activity.

Yes, bananas that have turned completely black are still safe to eat. While they may not be aesthetically pleasing, the fruit’s flesh is still nutritious and edible. However, if the banana has any mold or a strong fermented odor, it should be discarded.

The ripeness of the banana when purchased, the temperature during storage, and the presence of other fruits can all impact how quickly a banana ripens and turns brown. Ethylene gas, emitted by many fruits including apples and tomatoes, will accelerate ripening, so keep bananas away from these fruits to slow down the process.