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Roots and tubers from Andean Altiplano

Chuño and tunta (freeze-dried potato) - boundary entrych'uñu

Chuño is potato preserved by freezing it outdoors at night, thawing it in the sun, trampling out the water and drying it, which is a physical process, not a fermentation. Black chuño is dried without washing. White chuño, called tunta, also soaks for weeks in running water, which leaches out bitter glycoalkaloids before it is dried white; no study has shown microbes doing this work.

Fully documentedRoots and tubers24 days – 33 days

Recipe

Chuño and tunta (freeze-dried potato) - boundary entry, a photo from Wikimedia Commons
Photo: Eric in SF, CC BY-SA 3.0, via Wikimedia Commons
No fixed amounts recordedField practice with no fixed amounts.
PotatoesBitter, frost-hardy kinds are the ones whose glycoalkaloids are leached out[valdivieso2026]
Running waterFor tunta only; a pond or pool fed by a stream[cocarico2026]

Total time across the recorded steps: 24 days – 33 days

Start
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-16–-1 °CHumidity 25–40 %

What changes: Potatoes freeze outdoors at night and thaw in the sun by day

Step 1 of 5
Spread the potatoes out for night frost
Time
3 days
Reported
Temperature
-16–-1 °C
Reported
Salt
None given
Acidity
Not documented

Output: frozen and thawed potatoes.

Flavour
Not documented
Texture
tubers go soft and watery on thawing
Colour
Not documented

Microbes at work in this step

none; ice crystals break the cells

Method

Measured measured in a studySet fixed by a specification or tested recipeReported one source reports itTypical a general value, not sourced for this fermentUnconfirmed not yet checked against a source

At a glance

Chuño is potato preserved by freezing it outdoors at night, thawing it in the sun, trampling out the water and drying it, which is a physical process, not a fermentation. Black chuño is dried without washing. White chuño, called tunta, also soaks for weeks in running water, which leaches out bitter glycoalkaloids before it is dried white; no study has shown microbes doing this work. Made in 5 steps over 24 days – 33 days. The longest step, tunta: soak in running water, takes 21–30 days (Cocarico S 2026).

Key numbers
Main step21–30 daysReported[cocarico2026][inia]Tunta: soak in running water
Temperature-16–-1 °CReported[valdivieso2026]Spread the potatoes out for night frost

What makes this one different

This is a boundary entry. Chuño is preserved by frost, pressing and drying, and tunta adds weeks in water fed by running water, which leaches and washes it. Tocosh is a separate entry for Andean potato left in water on purpose. A household variant soaked in still water gives a darker, lead-gray product (Cocarico).

Related ferments

Variants

  • Moraya (muraya)Frozen potato soaked in semi-stagnant rather than running water, as its own entry sets out.
  • Household still-water tuntaA household variant of tunta submerged in still rather than running water gives a darker, lead-gray product (Cocarico).
  • KayaThe same freeze and soak method applied to oca, with water before or after freezing.

Safety

Soaking for tunta leaches part of the bitter glycoalkaloids from bitter potatoes into the water. Black chuño, which is not soaked, keeps some bitterness. These glycoalkaloids are toxic. An intake of 1 mg per kg of body weight or more can bring on vomiting, diarrhoea and stomach pain, and ordinary potatoes that taste bitter have measured 250–800 mg/kg (EFSA 2020). Boiling peeled potatoes removes only 5–65 %, so cooking alone is not enough for bitter tubers. No source read measures them in finished chuño or tunta, and leaching takes weeks, so do not eat bitter potatoes without this processing.

Hazards the sources name: Potato glycoalkaloids, high in the bitter Andean potatoes used and partly leached out in the tunta soak (plant toxins, not microbes).

History and sources

Every number is labelled with how it is known. How this atlas is made

Valdivieso and colleagues describe chuño as a preservation technology practised for centuries (Valdivieso 2026).

Starter
The sources we found do not say how any fermentation in it begins.
  1. [valdivieso2026] Valdivieso F., Vila J.L., Mollinedo P., Apaza Ticona L. 2026, Structural and functional effects of traditional chuño processing on potato starch (Solanum spp.), Foods 15(12):2180paper
  2. [cocarico2026] Cocarico S., Rivera D., Beck S., Rivera-Obón D.J., Obón C. 2026, From tradition to nutrition, wild and cultivated Aymara food plants as sustainable resources in the Andean neotropics of Bolivia, Frontiers in Nutrition, doi:10.3389/fnut.2026.1826362paper
  3. [ortiz2026] Ortiz-Sempértegui J. et al. 2026, Functional characterisation of traditional Andean freeze-sun dried potato derivatives, chuño and tunta, Food Chemistry 502:147760 (abstract)paper
  4. [inia] INIA Peru, Arcos et al., Variedades de papas nativas para procesamiento de tunta (citing Fonseca et al. 2011)paper
  5. [efsa2020] EFSA CONTAM Panel 2020, Risk assessment of glycoalkaloids in feed and food, in particular in potatoes and potato-derived products, EFSA Journal 18(8):e06222gov
  6. [wp] Wikipedia, Chuño (outline only)wiki