How to Store Bananas in Summer: 13 °C (56 °F) Is the Line Below Which the Peel Suffers
Bananas are damaged by cold below 13 °C (56 °F), while a summer kitchen at 25 °C (77 °F) cuts ripening from ten days to four. When to keep them out, when to refrigerate and how to freeze overripe fruit.
Below 13 °C (56 °F) bananas are damaged, and a home fridge runs at 4 °C (40 °F)
The optimum temperature for holding green bananas is 13 to 14 °C (56 to 58 °F) at 90 to 95 % relative humidity, according to the USDA's Agriculture Handbook 66 (chapter "Banana and Plantain", 2016). The same source defines chilling injury as the result of exposure to temperatures below about 13 °C (56 °F), occurring after anywhere from a few hours to a few days, depending on cultivar and ripeness. Green fruit is slightly more sensitive than ripe fruit.
The FDA says a home refrigerator should run at 40 °F (4 °C) or below, nine degrees Celsius under the banana's limit. The USDA lists the symptoms: brown or black streaks under the peel, a dull, grayish cast on the skin and failure to ripen; in severe cases the peel turns black and even the flesh browns and develops an off taste. The damage is not visible immediately but 18 to 24 hours after it occurs. That is why supermarkets display bananas away from the chilled shelves: the USDA states plainly that refrigerated shelf space is too cold even for ripe fruit.
A summer kitchen works like a ripening room
Commercially, bananas are ripened at 14 to 18 °C (58 to 64 °F), occasionally up to 20 °C (68 °F), at 90 to 95 % humidity. Handbook 66 also gives the speed: above 18 °C (64 °F) the ripening cycle takes only 4 days, while at 14 °C (58 °F) it stretches to 8 to 10 days. Above 25 °C (77 °F) you get what growers call "cooked fruit": the pulp softens while the peel stays green. In a flat that sits at 26 to 30 °C (79 to 86 °F) in summer, bananas bought more green than yellow (stage 3 on the 1-to-7 colour scale, where 6 is fully yellow and 7 is yellow with brown flecks) become speckled within a few days.
Respiration shows how much heat accelerates the process: a ripe banana at 13 °C (56 °F) gives off up to 80 mg of CO₂ per kilogram per hour, and at 20 °C (68 °F) up to 280 mg, three and a half times more. The practical rule that follows: in summer buy smaller quantities, choose fruit with green tips and keep it in the coolest spot in the home that is not the fridge, away from windows, the hob and the oven.
Ethylene: bananas both produce it and react to it
According to the USDA, bananas respond to ethylene at concentrations as low as 0.3 to 0.5 µL per litre of air, and a ripe banana itself releases up to 5 µL of ethylene per kilogram per hour (measured at 15 °C / 59 °F). A tomato releases about 10 µL, a ripe avocado more than 100, and an apple an amount that "varies greatly" with variety and ripeness. Two rules follow: keep bananas you want to slow down away from the bowl of apples, tomatoes and avocados, and put bananas you want to hurry along in a closed paper bag with one ripe apple, because the gas accumulates inside closed packaging.
When a ripe banana may go in the fridge after all
Handbook 66 recommends that ripe fruit be held "to a minimum", and the fridge is the only way to stop ripening at home. A fully yellow banana (stage 6) will darken on the peel in the fridge, because the skin of ripe fruit is also prone to chilling injury, but the flesh stays firm for a few more days. Peel and eat it as soon as you take it out: the USDA notes that chilled ripe fruit turns dull brown once returned to warmth and becomes sensitive to the slightest pressure.
Sliced bananas count as perishable food. The FDA rule: food that needs refrigeration must not sit at room temperature for more than 2 hours, and if the room is above 90 °F (32 °C) the limit is 1 hour.
| Fruit condition | Where | Duration (source) |
|---|---|---|
| Green (stage 1–3) | 13–14 °C (56–58 °F), coolest spot in the home | ripens in 4 days above 18 °C (64 °F), 8–10 days at 14 °C (58 °F) (USDA HB 66) |
| Yellow (stage 6) | fridge 4 °C (40 °F), peel on removal | "to a minimum"; peel darkens, flesh stays firm (USDA HB 66) |
| Sliced | closed container, fridge | max 2 h out of the fridge, 1 h above 32 °C (90 °F) (FDA) |
| Overripe, mashed | freezer −18 °C (0 °F) | best quality 8–12 months (NCHFP), safe indefinitely (FDA) |
Overripe bananas: mash, add vitamin C, freeze
The National Center for Home Food Preservation (University of Georgia) prescribes this procedure: take ripe but still firm bananas, peel and mash them thoroughly, then stir half a teaspoon (1,500 mg) of ascorbic acid into each cup (240 ml) of mash to prevent browning. Seal the mash in a moisture-vapour-resistant container and freeze. Fruit and vegetables keep their best quality for 8 to 12 months at −18 °C (0 °F), and the FDA adds that frozen food stays safe indefinitely, only its flavour declines with time. The mash goes straight into banana bread batter, pancakes or a smoothie; you will find banana recipes at jelo.hr/recepti.
Izvori
- USDA ARS, Agriculture Handbook 66: The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks (2016), chapter "Banana and Plantain"
- FDA, Refrigerator Thermometers – Cold Facts about Food Safety
- National Center for Home Food Preservation, Freezing Bananas
- National Center for Home Food Preservation, How Long Can I Store Frozen Foods