Why Do Bananas Turn Brown? [and In Other 9 Colors]
What big herbs can be grown indoors? There’s the giant Italian parsley (Petroselinum crispum ‘Géant d’Italie’), giant sage (Salvia disermas L.), and the giant fennel (Ferula communis), which grows up to 10 feet. But nothing beats the biggest herb in the world: the banana, which comes in many colors.
Bananas colors depend on two factors: maturity and species. Bananas get 1) brown/black while ripening, 2) green if unripe, or 3) yellow if ripe. Depending on the species there are 4) red (Musa acuminata ‘Red Dacca’); 5) pink (Musa velutina); 6) scarlet (Musa coccinea); 7) blue (Musa acuminata × balbisiana ‘Blue Java’); 8) orange (Musa balbisiana), 9) purple (Musa violacea), or 10) striped bananas (Musa ae ae).
Even more unique: the banana tree is not a tree – it’s an herb. The fruit is not a fruit or a vegetable – it’s a berry. The stem or trunk is not what you see — the real stem grows underground, horizontally (like ginger).
And that’s not all!
Bananas come in different colors, and each color tells us many useful things. Here’s what you need to know.
FACTOID: There are seven color index numbers from “green” to “yellow flecked with brown” on the USDA Banana Ripening Guide.
Why Banans Turn Green?
Unripe bananas are starchy and green because of high chlorophyll levels. When bananas become mature, the ripening process begins and a hydrocarbon gas called ethylene converts the starch into sugars, softens the fruit, and breaks down the green chlorophyll into the color of ripeness.
Green bananas provide many health benefits, vitamins and nutrients. They shouldn’t be eaten raw as they don’t taste good and they’re hard to digest. However, they can be cooked in many different ways.
Meaning 1: They’re good for you: Green bananas contain Vitamin C and Vitamin B6; a hundred grams of raw bananas includes almost 3 grams of fiber, which helps in indigestion and aids in constipation. The high amount of pectin and resistant starch (soluble fiber) in green bananas also provide many health benefits.
Meaning 2: They’re health food: When boiled, one cup of green bananas contains about 531 milligrams of potassium, which is important for the heart to beat regularly, for the nerves to feel, for muscles to relax and contract, for removing waste from cells, for bringing nutrients to cells, and to protect you from the effects of too much salt in your food.
Meaning 3: Don’t eat them raw: For instance, green bananas are (a) unripe bananas that will turn yellow when they’re ripe; (b) a type of starchy banana that’s cooked like a vegetable; (c) they’re not sweet so they have low sugar content; and (d) it takes longer to digest them.
Meaning 4: Cook them in different ways: For easier digestion and better enjoyment, green bananas are cooked and served in different ways. They can be boiled or steamed. They can be batter-fried, deep-fried, or stir-fried. Green bananas can also be curried, mashed, or used as a stuffing in pastry or a meat dish.
As bananas ripen, the starches transform into sugars, and the banana skin turns yellow. Let’s see how this helps us.
Why Bananas Are Yellow?
Immature bananas show a variety of green colors, from light green, silvery green, to dark green. They turn yellow because a) they’re climacteric berries (not fruits), b) the temperature is high, or c) ripened by ethylene and polyphenol oxidase.
Meaning 1: Bananas are climacteric: Bananas turn yellow because they’re climacteric berries (yes, they’re not fruits). Climacteric berries produce a lot of ethylene and continue to ripen after they’re separated from the mother plant.
Meaning 2: Bananas feel the heat: Bananas ripen and change their color when the temperature is above 57° F (13.8° C). The warmer the temperature, the sooner bananas will ripen and get darker in color. Thus, refrigerated bananas will darken much more slowly. This is why, when bananas are left outside, they turn yellow to brown in a few days.
Meaning 3: Bananas have the enzymes: Bananas turn yellow when they produce ethylene as well as an enzyme called polyphenol oxidase (which is also found in apples, potatoes, and pears). These react with oxygen and cover the banana skin with a kind of rust that produces a darker color from yellow to brown.
Meaning 4: Bananas are of different species: Some bananas turn red, orange, or maroon when ripe. Banana species that turn yellow when ripe include the silk banana or latundan (Musa acuminata balbisiana), the lakatan (Musa acuminata lakatan), the the bungulan (Musa acuminata masak hijau), French plantain (Musa × paradisiaca) and the well-known Cavendish bananas (Musa acuminata Cavendish), often sold in groceries and supermarkets.
PRO TIP: In a paper bag, bananas can ripen within 12 to 24 hours. On your counter, bananas can ripen within 2 to 6 days, depending on the room temperature. In the fridge, ripening slows down a bit, so it can take about a week or less.
Why Bananas Turn Brown?
As a general rule, bananas turn brown as the enzymes react with oxygen and break down the starches into even more sugars and antioxidants. Ripening can be hastened or delayed by interventions such as temperature, ethylene, or oxygen.
Meaning 1: Unpeeled bananas ripen: About three to five days after ripening, the banana peel naturally produces ethylene, which creates brown spots and continues to do so as long as it is unpeeled. The flesh inside can also show brown spots but are mostly safe to eat.
Meaning 2: They’re sweeter – Brown bananas have higher sugar content than when they were yellow, so diabetics or those who need to watch blood sugar should avoid eating these. On the other hand, there are those who prefer the extra sweetness of bananas with brown skin spots.
Meaning 3: They’re still good – After peeling, high levels of ethylene degrade the yellow pigments on banana skins (enzymatic browning). Brown bananas contain tryptophan that can help to reduce anxiety and stress. In addition, brown bananas are rich in nutrients that develop healthy bones and muscles.
Meaning 4: They’re useful in many ways – Bananas that are brown and soft are the most convenient snacks. Add them to smoothies, cereals, muffins, cakes, and other desserts. When baking, you can also use brown bananas instead of sugar.
FACTOID: The world’s largest herb is the Musa ingens, a wild banana plant that can grow up to 15 feet tall.
7 Methods To To Speed Up Ripening
There are at least six (6) ways to speed up the ripening of bananas.
Use a Paper Bag: To ripen bananas faster, put them in a paper bag with some ripe bananas. Fold the bag’s top loosely, and presto: the bananas should ripen in a couple of days.
Counter Exposure: Don’t refrigerate, don’t wrap – just place them on your kitchen counter. Exposure to oxygen and warm room temperature will make bananas ripen faster. In a warm room, bananas can ripen within 24 to 48 hours.
Separation: Many of our readers swear that separating the bananas from the bunch and wrapping each one separately can hasten ripening. Others say this doesn’t work, or it takes bananas in a bunch from 1 to 2 days before they ripen. Have you tried it? Let me know.
Ripening fruits: Other berries and fruits produce ethylene when ripening. Place your unripe bananas near these ethylene producers, and you’ll see faster ripening of the bananas. In a paper bag with ripening apples or pears, bananas should ripen in a day or two.
Sunlight exposure: Exposing bananas to direct sunlight can increase the temperature inside the flesh. This can “cook” the banana and result in faster ripening, but it may not be as sweet as naturally ripened bananas. For slower and more even ripeness, keep bananas at room temperature, away from direct heat or sunlight.
High heat: Bake the bananas at 300°F for about 15 minutes or until the peel turns black, and you’ve got ripe bananas for baking. Alternatively, you can use a fork to punch holes in the banana, and then microwave on high for 2 minutes or more.
5 Methods To Delay Ripening
There are at least six (6) ways to prevent premature ripening or delay the ripening process of bananas.
Isolation: Keep bananas far away from tomatoes, avocados, apples, peaches, and figs as well as other ripening fruits and veggies.
Freezing: To keep your ripe bananas for the longest time (up to 30 days), freeze them. They make great cookies, smoothies, or pancakes after defrosting. Freezer bags can prevent freezer burn.
Sealing: Reduce oxygen contact by vacuum packing, airtight containers like ziplock bags, or wrap the stem (crown) in the plastic where the ethylene is produced.
Sour bath: Lemon juice, vinegar, or sulfuric preservatives such as salicylic acid can counteract the oxygen’s oxidizing process on the enzyme. Likewise, add citrus drops such as juice of lemon, orange, pineapple, or lime (diluted with water is ok, too) so that peeled bananas don’t turn dark.
Temperature change: Heat can deactivate the enzyme. Cool temperatures can slow down the ripening process. The flesh remains okay even if pigments in the peel turn dark.
PRO TIP: Hang your bananas to prevent bruising. To delay ripening, get a separate banana hanger such as this one from Amazon and store in a cool place. However, for faster ripening, use a fruit bowl with a banana hanger like this one, also from Amazon, and leave it in a warm room with some ripe apples or pears in the bowl.
Black Bananas: Meanings You Should Know
When a banana turns black, it’s either oxidized, too ripe, or diseased. To simplify:
(a) overripe banana: yellow skin with blackened spots spreading all over;
(b) diseased banana: unripe, with blackened ends or soggy or rotting black areas spreading;
(c) oxidized banana: exposed to a lot of air (oxygen).
Meaning 1: It’s the cold: Cold air – whether winter air, the air in the freezer or in the fridge – separates the cell walls of banana peels. At the same time, enzymes (polyphenol oxidase) in the peel react with oxygen and produce melanin, which turns the peel brown or completely black (similar to how suntanning increases the melanin on our skin).
Meaning 2: Too much air: Bananas that turn black when frozen or refrigerated indicate that they were exposed to too much air (oxygen) before they cooled down.
Meaning 3: They’re healthy food: Very overripe bananas with black peel are still good to eat when the flesh is not damaged. They’re rich in antioxidants that delay or even prevent cell damage in our bodies. Antioxidants prevent oxidation (reactions with oxygen) that creates chain reactions and free radicals that damage body cells.
Meaning 4: They’re great snacks: Overripe bananas are great for quick muffins, breads, puddings, and cakes. They’re perfect for milkshakes, cookies, pancakes, and smoothies. They also go well with oatmeal and ice cream.
Meaning 5: They’re roasted: When bananas are roasted in the peel (unpeeled), the peel turns black from the high heat, at the same time protecting the cooking flesh inside. Use a fork to peel and cool the cooked flesh.
Meaning 4: Throw them away: Diseased bananas may have been attacked by the Black Center Syndrome, or by a fungus called nigrospora, where the center turns very dark red. Some sources say that dark flesh in the banana may be caused by polyphenol oxidaze, a derivative of benzene, which is harmful to human health.
FACTOID: A cooking banana is prepped and cooked (not ripened) before it is eaten. It is starchy with thick, green skin before it ripens. Cooking bananas are prepared as desserts or vegetable dishes or may be ground into flour.
Other Banana Colors (From Red To Orange)
Aside from green, yellow, brown, and black, bananas also appear in other colors. Here’s a shortlist of banana colors and what each one signifies.
Red Bananas (Musa acuminata ‘Red Dacca’) are sweet and, except for the Red Cavendish banana, are named for where they grow: Red Colorado, Red Cuban, Red Jamaican, or Red Spanish bananas. All red bananas are rich in iron and potassium but have more beta carotene, magnesium, vitamins C and B6 compared to yellow bananas. They’re also sweeter, softer, and have a longer shelf life than yellow bananas.
FACTOID: The blood banana (Musa acuminata var. zebrina) is grown as an ornamental plant with dark red patches on green leaves. It can be grown in containers and bears small, slender edible fruit-like berries that contain small, grape-like seeds.
Pink bananas (Musa velutina) have hairy or fuzzy skin that peels back when the fruit-like berries are ripe. The seeds are said to take up to 6 months before they sprout. In fact, before sowing, seeds are first soaked in warm water for at least 24 hours.
Scarlet bananas (Musa coccinea) are red flowering bananas that are native to Vietnam and China. The 2-cm (0.8 inch) orange berries are not edible but they’re favorite ornamentals.
Blue bananas (Musa acuminata × balbisiana ‘Blue Java’) are light blue to sky blue in color when unripe, and turn into pale yellow with silvery hues when they ripen. Also called Hawaiian banana or ice cream banana, their bluish-green color and ability to withstand cold weather make them a favorite garden ornamental plant.
Orange bananas (Musa balbisiana) are plantains, which are bananas for cooking rather than for ripening. The seeds of edible fruits are dark, while the leaves are used for crafts and wrappings. In the Ryukyu Islands of Japan, the leaves are used to make basho cloth.
In addition, the fruit-like berries can be pickled when young before seeds develop. The male flower is cooked and eaten as a vegetable. Orange bananas are sometimes mistakenly called blood bananas (Musa acuminata var. zebrina)
Copper bananas (Musa troglodytarum) are also known as Fehi or Fei bananas. The banana skin colors range from red to brilliant orange with either orange or yellow flesh inside, which is cooked before eating. Fei bananas look very different from other banana species. For instance, it’s the only banana that fruits upwards – all other bananas fruit downwards.
Violet bananas (Musa sikkimensis) are also known as Darjeeling bananas. They grow in high altitudes in India, Bhutan, and at the foot of the Himalayas. The small violet berries are sweet when ripe. Another violet-skinned banana is the Musa itinerans or Burmese blue banana.
Purple bananas (Musa violacea) are ornamental plants with violet flowers (often used in flower arrangements), as well as 3-inch violet fruit-like berries. This small banana plant is a favorite among houseplant enthusiasts.
Striped bananas (Musa ae ae) also known as variegated banana or Royal Hawaiian, have white and green striped leaves and berries. When ripe, the berries turn golden yellow, or bright yellow-orange. The fruit-like berries in a bunch can ripen individually — not together, like other banana species do.
FACTOID: From the late 60s to the early 70s, many believed that a short-lasting psychedelic can be derived from Musa sapientum bananadine. Not just hippies but academics, publishers, students, wire services, news media, even the FDA.
PRO TIP: If you’re growing banana plants indoors, make sure to provide 12 hours of bright light, well-drained humus-like soil, and keep temperatures controlled to prevent burning or scorching.
Takeaways
The banana is the world’s biggest herb, so big that it’s often called a “tree” by mistake. Their berries are often called “fruits” with colors that indicate species or stages of ripening.
Green bananas are unripe while yellow bananas are ripening. Yellow bananas with brown spots are already ripe, while dark bananas are overripe, oxidised, or diseased. Overripe or oxidised bananas can be used for dessert such as smoothies or baking, but diseased bananas should be thrown away .
Bananas of various species also bear fruit in different colors including red, pink, violet, blue, orange, purple, or even striped. Most of these turn bright yellow or bright orange when ripe. There are several ways to delay as well as to hasten the ripening of bananas.
And that’s it! You’ve just completed a review of the colors of bananas. Do you have a growing bananas story to share? Do tell. I’d love to hear it.
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Sources
“Banana Ripening Guide” by USDA (AMS)
“Ripening Bananas Glow An Intense Blue Under Black Light” by S. Mosher et al in Science Daily
“5 Genius Ways to Quickly Ripen Bananas” by A. Savares in Spoon University
“Delayed Ripening Technology” by International Service for the Acquisition of Agri-biotech Applications (ISAAA)
“Delayed ripening of banana fruit by salicylic acid” by M. K. Srivastava & U. N. Dwidevi in Plant Science
“The taxonomy and origins of the cultivated bananas” by N. W. Simmonds & K. Shepherd in Botanical Journal of the Linnaean Society
“Why Do Bananas Change To Yellow When Ripening?” by B. D’Mello in Science ABC
“Banana medicinal uses” by N. Jyothirmayi & N. M. Rao in Journal of Medical Science and Technology
“Medicinal benefits of Musa paradisiaca (banana)” by N. Rajesh in International Journal of Biology
“Banana (Musa spp) from peel to pulp: ethnopharmacology, source of bioactive compounds and its relevance for human health” by A. Pereira & M. Maraschin in Journal of Ethnopharmacology
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