How long to dehydrate bananas

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Last reviewed August 2026.

Plan on 6 to 10 hours at 140°F for ⅛-inch banana slices. That is not one source's guess — North Dakota State University Extension's fruit-drying table says to cut bananas in "1/8 inch slices" and "dry until tough and leathery (6 to 10 hours)", and Colorado State University Extension lands on the same 6–10 hours at the same 140°F (60°C). Two extension services, independently published, same window. The width of that window is the honest part: four hours of spread is the difference thickness, humidity and airflow make, and no dehydrator can narrow it for you.

Nesco, Excalibur, Ninja — the badge is not what sets the time

The most-searched versions of this question name a machine. They shouldn't. Every thermostatically controlled dehydrator holding 140°F is doing the same thing to the banana: keeping it at drying-record temperature while moving air past it. A high-airflow unit like the Nesco FD-1040 Gardenmaster or the Excalibur 3926TB finishes near the 6-hour end; a quieter one sits nearer 10. What does change the answer is whether your unit has a dial at all — a fixed-preset model that only runs around 165°F is holding jerky temperature over fruit, which is how you get a dry shell over a wet centre.

A Ninja air fryer on its dehydrate setting is a small chamber with a strong fan. It will crisp a single layer of thin banana faster than a stacked dehydrator will, and it holds a fraction of the bananas. Treat its clock as unrelated to the 6–10 hours above and watch it, because a fast fan takes slices past leathery quickly.

"At 135 degrees", and drying bananas in the oven

135°F is fine. Extension fruit-drying guidance sits in the 135–140°F band; 135°F simply runs at the slower end of the range. Going the other way is the risk, not the caution: NDSU puts oven drying at 140 to 145°F specifically to avoid case hardening, where the outside seals before the middle is dry and the trapped moisture spoils the batch in storage. An oven works on the same logic as a dehydrator — lowest setting, door propped for airflow, and expect it to run long, because most ovens do not go low enough to be gentle and do not move air the way a dehydrator does.

Why banana slices brown, and the ten-minute fix

Banana oxidises fast on a cut face. NDSU's table says to dip the slices in "citric acid or other anti-darkening/anti-microbial solution for 10 minutes" before drying; CSU lists the same family of options — "an ascorbic acid, citric acid, lemon juice or sodium metabisulfite solution". This is cosmetic, not a safety step, and skipping it costs you colour rather than the batch. Slice evenly while you are at it: a tray of ⅛-inch rounds finishes together, a tray of mixed thicknesses gives you scorched thin ones and damp thick ones at the same moment.

Chewy slices vs crisp banana chips

These are two different targets, and the split is thickness and time — not a hotter dial.

• Tough and leathery — the doneness extension guidance actually specifies, and the one to store. NDSU's test: "The pieces should spring apart when released. Cut several cool pieces in half. You should not see any moisture, and the fruit should not be sticky."
• Crisp chips — cut thinner and leave them in longer at the same 140°F, until they snap rather than bend. Note that the shop-bought banana chip you are picturing is usually fried in coconut oil, not dried; a dehydrator will not reproduce that texture no matter how long you run it, and that is a recipe difference, not a machine failure.

The step after the machine stops — and where the sources disagree

Dried fruit is meant to be conditioned: packed loosely in jars, lightly covered, stirred or shaken daily so the moisture left in the batch equalises before it is sealed away. It is the most-skipped step and the reason a "perfectly dried" jar grows mould weeks later.

On how long, the record is not unanimous, and it is worth saying so rather than picking one: CSU says "four to 10 days", NDSU says "four to seven days". Nobody is wrong — it is a judgement window, and the instruction that matters in both is the same, which is to keep looking for condensation on the glass and put the batch back in the dehydrator if you find any.

Sources — read them yourself

• NDSU Extension — Food Preservation: Drying Fruits (Table 1: bananas ⅛-inch, 6–10 h; oven 140–145°F; doneness test; conditioning 4–7 days)
• Colorado State University Extension — Drying Fruits (140°F; bananas 6–10 h; pretreatment; conditioning 4–10 days)
• NCHFP — Drying foods at home

Gear these methods assume — a citric or ascorbic acid dip is what keeps banana slices from going grey while they dry. Restocking? On Amazon ↗. Paid link; it changes nothing in the record above.

Related: apples · strawberries · blueberries · peaches · pears · orange slices · why fruit dries at ~135–140°F, not 165°F.

Dehydrator Score indexes published specs and marketing claims against the USDA/NCHFP record, with attribution — we test nothing and give no safety advice. For drying guidance use NCHFP or your extension office. If a source changes, the page changes — the record wins.