What is Happening As Bananas Ripen?

Malcolm Tatum
Malcolm Tatum

Just about everyone who buys bananas knows that the fruit can move quickly from being firm with a green peel to being soft with a mottled brown and yellow peel. There are several processes that are at work on both the chemical and nutritional value of the fruit, as well as the texture of the peel. As bananas ripen, the peel releases nutrients into the fruit, and the starch begins turning to sugar.

Bananas at various stages of ripeness.
Bananas at various stages of ripeness.

One of the first things people tend to notice is the change in the color and thickness of the peel that covers the fruit. Just as changes are taking place inside, shifts in the composition of the peel are occurring. As the banana develops, the peel acts as a housing for chlorophyll that is manufactured as a result of the direct sunlight required to grow the fruit. As the interior fruit reaches peak condition, the green peel that had been absorbing all that sunlight begins to undergo a chemical change that helps to mellow the fruit. As a result, the interior of the peel releases nutrients into the fruit that enhance the sweetness.

Banana stalk.
Banana stalk.

At the same time, the peel begins to lose chlorophyll content and changes from green to yellow. During this transformation, the peel itself begins to deteriorate, leaving behind only a thin covering that can be peeled away from the mature fruit with ease. Since bananas ripen quickly, it does not take long to go from a bitter green to a sweet yellow fruit.

Bunch of bananas.
Bunch of bananas.

On the inside, important things are happening at this time. During the earlier stages of the maturation process, the fruit has a distinctly tangy flavor that lacks sweetness. For some, the fruit at this stage is almost bitter. As the banana reaches maturity, and the interior of the peel begins to release nutrients into the fruit, however, changes take place. The starch found in the inner linings of the peel and in the fruit proper convert into simple sugars that work through the fruit, leaving a texture that is softer and considerably sweeter.

Strictly speaking, there is no one ideal stage to consume this fruit, and various modes of preparation call for ripening bananas at varying states. When cooking the whole fruit, green bananas are usually preferred, due to their firm nature. For general consumption as a snack or in a cold dessert, one that is yellow and still firm is considered ideal. For use in cooked recipes, such as banana bread, it's best to use those that have become soft and feature a peel that is mottled brown with yellow. Since bananas ripen and are harvested at various stages, it is relatively easy to purchase them at any point in the maturation process.

Red bananas.
Red bananas.
Malcolm Tatum
Malcolm Tatum

After many years in the teleconferencing industry, Michael decided to embrace his passion for trivia, research, and writing by becoming a full-time freelance writer. Since then, he has contributed articles to a variety of print and online publications, including wiseGEEK, and his work has also appeared in poetry collections, devotional anthologies, and several newspapers. Malcolm’s other interests include collecting vinyl records, minor league baseball, and cycling.

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Discussion Comments


The astringent or harsh taste of green bananas is due to their polyphenols.


Green bananas are very high in starch that resists digestion (called resistant starch). Dried green bananas can contain up to 70 or 80% resistant starch. As the banana ripens, the starch is broken down and converted into sugars. A yellow banana with green tips will still contain about 15% resistant starch while a fully yellow banana with brown spots has only 1-2% resistant starch. Resistant starch is a prebiotic insoluble dietary fiber that feeds the bacteria that live in our large intestines (called microbiota).


To make bananas ripen faster put them on a cookie sheet in the oven at 170 F for about half an hour, keep an eye on the oven. Cool, peel and use in your recipe. I wanted to make muffins, but my bananas were not ripe enough. I tried this method and it worked great.

While the bananas are ripening I prepare the rest of the ingredients. Now I can bake when I want, and do not have to wait around for bananas to ripen on their own which takes days sometimes.


I know this sounds crazy but this article was great. I had to do an experiment in my science class and explain what was taking place during the ripening of a banana.


@anon268876: Fructose is part of a formula that creates glucose. Therefore the fructose isn't simply turning into glucose. It is, in fact, forming a bond with another monosaccharide. This therefore means instead of merely 'changing,' it forms a bond classified as glucose.


At what point do bananas start to ferment?

I definitely prefer my bananas very ripe - more than half-brown is just the beginning of a "good" banana, to me! No more of that alum-like puckering that a green or yellow-only banana has.

But, I also appreciate the liqueur-like taste of an all-black banana. (My wife has finally learned to not throw them out on me!) I'll eat them straight up like any banana, and they work wonders in plain full-fat yogurt due to their extreme sweetness. (Add real peanut butter and/or cocoa powder for variations.)

But, I am curious if I'm getting any sort of alcohol at this point? I am not an alcoholic and I know it would be minuscule if any, so no worries about getting drunk at work! It is just curiosity mostly. Has it started to ferment by this point?


I believe that during the ripening process and the banana turns brown the sugar profile changes from fructose to glucose. The sugar is then easier to use with the body and the liver.


Why do bananas ripen slower when you put them in sealed ziplock plastic bags?


Once bananas are ripe and spotted, putting them in the refrigerator will preserve them for a week. They'll turn black but inside will be fine. And even black bananas that are practically soup make excellent banana bread.


Developing a preference for spotted bananas has the benefit that you will get more bananas -- since a lot of people just ignore them once they are spotted, it's easy to ask "hey, you want these spotted bananas?" and ta-da! You get 'em. At least that works for me at my brother-in-law's house.


its weird because im in the eighth grade and i am doing this for my science fair project!


this is pretty much what i learned in eighth grade for my science fair project.


I only like bananas when they're still green (I mean green green- the peel is still almost impossible to separate from the fruit) and have been trying to figure out exactly what I'm craving because the texture is horrible!


This is unusual, since many people use bananas to settle an upset stomach. If only well ripened bananas cause her discomfort, perhaps the amount of nutrients released by the peel into the fruit is more intense that when the banana peel is still yellow and the fruit is still somewhat firm. Have you mentioned this problem with excessively ripe bananas to your doctor?


Hi: I have a question; my wife eats bananas often, however when they ripen and are too spotted, they upset her stomach. I was wondering what causes this.


This site is awesome! It has helped me so much with research. I recommend this site to a lot of my friends when they need help. A++++++ for this site!

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