How to choose and store sweet potato (madhurakizhangu)

By the Cochimart Kitchen Desk · Published 29 October 2026

Madhurakizhangu: the short answer

Good sweet potato, madhurakizhangu (മധുരക്കിഴങ്ങ്), feels firm and heavy for its size, with smooth, unbroken skin and no soft spots. At home, keep the roots whole and unwashed in a cool, dark, airy place, in a basket or a paper bag, and use the softer ones first. The one place not to keep them is the fridge: unlike many vegetables, a raw sweet potato is injured by cold, so the fridge makes it worse, not better.

The name means "sweet tuber". You will see it on our vegetable names list, next to its look-alike in the shop, the ordinary potato.

The names you will hear

Do not confuse it with kappa, which is tapioca, or with the true yams, kachil and chena. The sweet potato (Ipomoea batatas) is the swollen root of a trailing vine in the morning glory family. Wikipedia notes it is only distantly related to the potato and even further from real yams, which is one reason it behaves differently in storage. Our tapioca guide covers the other everyday root.

When sweet potato is harvested in Kerala

Malayalam Wikipedia, citing the farming magazine Karshakasree, says Kerala growers usually plant in June to July and again in September to October. Where water is available, uplands are planted in October to November and paddy fields in January to February. The crop is normally ready three and a half to four months after planting, and yellowing leaves are the sign. Adding those months together, the main harvests fall around October to November, January to February, February to March and May to June, so roots are on sale in most of the year. This is our own arithmetic from the planting windows, not a published harvest calendar.

The same source gives a useful test for a farmer that applies to shoppers too: immature roots show a green tinge when cut. Local names it lists include Bhadrakali chuvala, Kottayam chuvala, Chinnavella, Chakkaravalli and Anakkomban, alongside newer improved varieties such as Sree Nandini, Sree Vardhini, Sree Ratna, Sree Bhadra, Sree Arun, Sree Varun and Sree Kanaka. Names change from district to district, so describe the skin and flesh colour you want instead of relying on one name.

Skin and flesh: what the colours mean

Wikipedia describes skin colours from beige through yellow, orange, red and brown to purple, and flesh from white and cream to yellow, orange, pink and deep purple. White or pale yellow types are less sweet and moist than red, pink or orange ones. That is useful at the stall: if you want a drier, more floury root, choose pale flesh; for a softer, moister, sweeter one, go for orange or reddish flesh. A seller will often cut one open if you ask.

Choosing sweet potato at the stall

• Press along the whole root. It should be hard everywhere. Any soft, sunken or damp patch is the start of rot, and rot spreads through the root.
• Look for unbroken skin. Skip roots with deep cuts, gouges or crushed ends. FAO stresses that damaged roots should not be stored at all, because damage lowers quality and lets disease in.
• Check the ends. Dried, clean ends are fine. Dark, wet or fuzzy ends are not.
• Choose medium, even roots. Very thin, pointed ends tend to dry out first, and one oversized root can hide a hollow or fibrous core.
• Avoid roots with long sprouts or shrivelled skin. They are old and have been losing water for some time.
• Prefer roots with a little dry earth over scrubbed, wet ones. Wet washed roots spoil faster in a hot kitchen.

Planning a week of shopping? Put madhurakizhangu on the bilingual grocery list so the stall owner gets the right name.

Why curing matters

Growers cure sweet potatoes after digging them, and it explains why a freshly dug root and a cured one behave differently. FAO describes curing as the roots' own wound-healing: held warm and humid for a few days, the damaged skin forms a layer of cork that seals cuts and bruises, keeps decay organisms out and cuts water loss. Wikipedia gives commercial figures for sweet potatoes: dry the freshly dug roots for two to three hours, then hold them at 29 to 32 °C with 90 to 95 per cent humidity for 5 to 14 days. After that, cured roots can keep for as long as 13 months in a store at 13 to 15 °C with humidity above 90 per cent.

You cannot reproduce that at home, and you do not need to. The practical lessons are these: buy roots that are intact, because curing cannot rescue badly damaged ones, and keep them away from cold, because the best storage temperature is a mild one, not a cold one.

How to store sweet potato at home

Whole roots: cool, dark and airy

1. Do not wash them before storing. Brush off loose soil and let any damp skin dry completely.
2. Lay them in a single layer or a shallow pile in a basket, open box or paper bag. Avoid sealed plastic bags and containers, which trap moisture.
3. Choose a cool, dark, ventilated spot: a shaded shelf, a cupboard away from the stove or a store room. Heat and steam from cooking speed up ageing.
4. Handle them gently. FAO notes that a damaged sweet potato's breathing rate roughly doubles about 20 hours after the wound, a sign of how fast injured roots start to age.
5. Check weekly and remove any soft root at once so it does not spoil its neighbours.

In a typical Kerala or Gulf kitchen, expect a couple of weeks for ordinary market roots, and longer in a cooler store room. That is a practical estimate, not a measured figure, because house temperatures vary so widely.

Why not the fridge?

Sweet potato is a tropical root, and FAO lists it among the crops that suffer chilling injury. Its handbook gives different thresholds in different passages, from about 12 °C and below down to under 5 °C, and says damage depends on both temperature and time. The symptoms include internal breakdown, more water loss, greater risk of rot, and changes in cooking quality and taste. They may not show while the roots are cold, only after they warm up again. A fridge runs well below those temperatures, so leave raw roots out of it.

Cut or cooked sweet potato

Once a root is peeled, cut or cooked, it is a perishable food and the usual rule applies: refrigerate it in a covered container, and use it within a day or two. Discard anything that smells sour or looks slimy.

When to throw sweet potato out

• Soft, mushy or leaking roots, or dark, sunken patches.
• Any mould, especially white or grey fuzz at the ends.
• A sour, musty or fermented smell, on the skin or when cut.
• Flesh that is dark brown or black through the root rather than in a small spot.

Small, dry sprouts and a slightly wrinkled skin mean the root is ageing, not necessarily spoiled: if it is still firm and smells right, cut away the sprouts and use it soon. A mild bad spot can be cut away generously, but if the rot has spread, the safest course is to discard the whole root.

For more root vegetables and everyday produce, see the Kerala season calendar, the drumstick guide and the full list of ingredient guides.

Sources and useful links

• FAO, Storage and processing of roots and tubers in the tropics, Chapter 2: Factors affecting storability of roots and tubers
• FAO, Storage and processing of roots and tubers in the tropics, Chapter 3: Principles of storage for roots and tubers
• Wikipedia: Sweet potato
• Malayalam Wikipedia: മധുരക്കിഴങ്ങ് (madhurakizhangu)

Frequently asked questions