Ingredient

Banana

A banana is one of the few fruits that genuinely improves for cooking as it gets past the point where you would want to eat it. The black, unappealing one on the counter is the correct banana for a loaf, and the firm yellow one is not.

What ripening actually does

A green banana is mostly starch. As it ripens, enzymes convert that starch into sugars — which is why a ripe banana is dramatically sweeter than a green one rather than slightly sweeter. At the same time pectin in the cell walls breaks down, so the fruit softens, and aromatic compounds develop that give ripe banana its distinctive smell.

All three changes point the same way for baking. More sugar means more sweetness and better browning; less structure means the fruit mashes smoothly and disappears into a batter; more aroma means the finished thing tastes of banana. A firm yellow banana in a loaf gives you chunks of blandness.

Ripeness, and what each stage is for

Green

Starchy, firm, barely sweet. Cooked as a vegetable in much of the world — boiled, fried, made into crisps.

Yellow with green tips

Firm and only lightly sweet. Best for slicing where you want the pieces to hold.

Even yellow

The eating banana. Sweet, soft enough, still holds together.

Yellow with brown freckles

Sweeter and more aromatic. The best eating stage for most people, and good in a smoothie.

Mostly brown or black skin

The baking banana. Very sweet, intensely aromatic, mashes to a purée. The skin looks worse than the fruit is.

Leaking, smelling of alcohol or fermenting

Past it. Throw it away.

Controlling ripeness

• To ripen faster, keep them in a closed paper bag at room temperature. They produce a lot of ethylene and trapping it speeds everything up. An apple in the bag helps.
• A very fast emergency version: bake unpeeled bananas at around 150°C for fifteen to twenty minutes until the skins are black. This softens and sweetens them enough for baking, though it does not fully replicate real ripening.
• To slow them down, separate the bunch — they ripen each other — and keep them cool and apart from other fruit.
• Freeze them when they get ahead of you. Peel first, because peeling a frozen banana is miserable. Frozen banana is the base of most "nice cream".
• Keep them away from anything you do not want ripened. A bowl with bananas in it ripens everything else in it.

The fridge question

Put a banana in the fridge and the skin turns black within a day. What has happened is chilling injury: cold damages the cell membranes in the peel and releases enzymes that oxidise phenolic compounds, so the skin browns rapidly.

The fruit inside is largely unaffected and ripens much more slowly, which means the fridge is actually a good way to hold a ripe banana at the stage you want it — as long as you can live with the appearance. What it does not do is help an unripe one: the cold also disrupts the ripening machinery, so a green banana chilled may never ripen properly afterwards.

Ripeness is the whole decision

• Green-yellow — firm, starchy, barely sweet. For frying, for plantain-style cooking, and for eating if you like them that way.
• Yellow — the eating banana. Sweet, aromatic, holds its shape.
• Spotted — sweeter still, softer, much more aromatic. The best for smoothies and for eating.
• Black — almost liquid inside, intensely sweet. This is baking ripeness, and a banana bread made with anything less does not taste of banana. See banana bread.
• To ripen fast, put them in a paper bag with an apple, which releases ethylene. To slow them, separate them and keep them cool.
• Freeze them peeled when they get ahead of you. They are then ready for baking or for ice cream, and it is the single best use for a fruit bowl gone too far.

Common questions