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I recently bought something that was labelled at the grocery store as a "purple sweet potato". They were larger than what I am used to for sweet potatoes, but looked similar, although they had a purple skin on the outside and white flesh on the inside. I figured since they were labelled as "sweet potatoes", I would prepare them the same way I like to prepare regular sweet potatoes, by boiling them first (for about 40 minutes), then removing the skin, slicing it into wedges and then pan frying them. I have done this many times with normal sweet potatoes, and it works quite well.

However, after I boiled the purple sweet potatoes for 45 minutes, I pulled them out to take the skins off, and they were soft and stringy and incredibly off putting - they felt the same way as a gummy mashed potato would feel, and they fell apart all over the place.

Are they more like a potato, requiring less boiling time? Or is there something else going on here that I am missing?

Edit: I went to the grocery store today, and they are now labelled as "purple yams". I don't know if that makes a difference or not. I also got a picture of them, to make my description a bit clearer. purple yams

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  • interesting... I've had purple potatoes before, but they were always purple inside.
    – nico
    Aug 1, 2011 at 19:30
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    Potatoes take max 20 mins, sweet potatoes max 15 minutes to cook. You are killing them!
    – TFD
    Aug 1, 2011 at 22:12
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    @TFD I was following a recipe that said to boil the sweet potatoes for 45 minutes - I have used it may times and the potatoes are still raw in the deep center after boiling, which is part of the reason you fry them, to finish cooking them.
    – user3058
    Aug 2, 2011 at 4:31
  • Those are "sweet potatoes" or here we call them Kumera.
    – TFD
    Aug 8, 2011 at 9:04
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    @TFD - I don't think chopping them is necessary. I don't chop regular potatoes or regular sweet potatoes, so I don't understand why these would be different.
    – user3058
    Aug 8, 2011 at 16:02

11 Answers 11

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I used to cook plenty of purple sweet potatoes when I was living in africa:) Sounds like you maybe cooked them too long...

They can be extremely tasty, sweet with a "perfumy" hint if you are lucky. They are best boiled with the skin on like you did and peeled afterwards (as the taste is preserved better that way). As for cooking time it really depends on the size (which means the potatoes are likely done at different times) but you can always feel when they are done by pressing on the potato with a fork - it should give slightly/be soft. I think it usually took me about 30min but I didn't use a clock. It may shorten the cooking time slightly to make holes in the potatoes with a fork (this also adds to the "creaminess").

I guess they do sometimes get a softer, more "creamy" consistency than your usual potato when well done. However the taste is richer and in my opinion far superior to orange sweet potato. If you prefer a firmer potato, just let your potatoes stay on the firm side (in my experience, though, the taste is enhanced by letting them go soft). But boiled ones would anyways mainly be for puddings as it gets rather sweet.

For panfrying I would suggest avoiding boiling the sweet pots first. Simply peel/wedge them raw, fry them as chips until done and serve with a spicy/hot dip - yum.

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These look a lot like some varieties of Japanese and Korean sweet potatoes, which often have purple skin and white flesh. I've found that they are drier and maybe starchier than orange sweet potatoes. They are hard to roast as they tend to dry out, but steaming or simmering in water work well, as does frying. If you search around for Japanese or Korean sweet potato recipes, I bet most of what you find will work well for these.

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Since sweet potatoes are usually classified by the color of the interior flesh, most parts of the world would call these white sweet potatoes. I think the easiest way to use these is to bake or to slice into half-inch thick circles, steam or boil about 20 min. After the initial cooking, you can also puree them with egg and coconut milk then bake similar to pumpkin pie, with or without extra elements such as crust, sweetener, spices.

I cook a lot of sweet potatoes - with flesh inside that is white, orange (sometimes called yams in US) and purple (Okinawan). I have noticed some variation in their handling.

Baking (in skin) 40 min @350F:

  • Orange are highest moisture and can be a little stringy, develop to a very soft consistency like cooked pumpkin.
  • White are somewhat like regular baked potato in texture.
  • Baking purple sweet potatoes tends to make them dry and starchy, hard to eat without adding liquid.

Steaming/boiling (peeled or not, cut into pieces) ~20 min:

  • Have not tried with orange sweet potatoes.
  • White and purple seem more starchy and can crumble/disintegrate if overcooked

Microwave: I have heard 5-8 min on high, and of course it depends on the machine, but I always seem to get undercooked spots. For me it works best with long narrow orange sweet potatoes, but not my preferred method.

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The purple skin sweet potatoes generally takes shorter time to boil in water that the white skin ones. You will find that it takes roughly the same amount of times as the golden skin potatoes which is roughly 15 minutes. They generally always becomes mushy once cooked by boiling. If you intend to pan fried or grill it, just let it boil for about 10 minutes, deskin after cooling and then pan fry it. In that way it will not be overly mushy. As a hint the best and sweetest taste are the purple skin sweet potatoes. The flesh is generally more grainy, fluffy and drier in texture and holds up better in form even being boiled.

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All yams are best when they are baked at 400 degrees F. Put them on a cookie sheet on top of a piece of foil to catch the drips. This is the best way to preserve the flavor and sweetness. They are done when the skin puffs up and they are soft to the touch. The purple yams are dryer than the orange ones, but they still have a nice flavor.

My favorite holiday yam recipe is to bake the yams, slice them into rounds, put in a baking dish and top with dabs of butter and melted orange juice concentrate drizzled over them like a sauce. You can make a day ahead then put the dish in the oven to warm 30 minutes before serving.

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The purple sweet potato according to materials I've researched had white flesh did you say? Well all white fleshed potatoes sweet or not are faster to cook usually about fifteen to thirty min.

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    Highly depends on the size of the potato. A small 50g potato does not take the same time as a huge 1kg monster...
    – nico
    Aug 2, 2011 at 5:51
  • @nico - that was my thinking. These sweet potatoes (or whatever they were, I'm not entirely sure) were pretty massive, so I cooked them for as long as I would cook a similar sized regular sweet potato, which I have done many times in the past.
    – user3058
    Aug 2, 2011 at 18:16
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When my wife first saw one of these, she cooked it like a regular sweet potato or yam, about 45 minutes or an hour in the oven at 350. It was as hard as a rock, so I figured we cooked it too long. The next time I bought one however, it had instructions stuck to it on the barcode label. As it turns out, you have to cook these much longer than a yam, 2 hours, plus you have to coat them in olive oil first and wrap them in foil....it may be a pain, but well worth it! One of the tastiest things I have ever eaten.

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I bought these purple yams by mistake and didnt know what to do with them. So I peeled them sliced them very thin, and placed them on a baking sheet. I drizzled olive oil, salt and pepper and roasted these for 20-25 minutes at 400 degrees. They were very good and tasted great.

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I was at my daughter's house today and she had bought these at the supermarket. She said they are labeled yams at the store. She wasn't sure what they really were or how to prepare them. She was boiling cabbages and carrots so we decided not to peel them and we quartered them and boiled them. We took them out when the center of the fleshy part was al dente. We did not remove the skin to eat and it was delicious. The skin was sweet but the fleshy part was just a little sweeter then a regular potato. We put a little goat cheese on them and oh my God they were out of this world! If you look up recipes for cooking Boniatos you will find many ways of cooking them.

From http://edis.ifas.ufl.edu/he610:

The boniato or tropical sweet potato, (Ipomoea batatas), also known as batatas or camote, is a member of the morning glory family. It is extremely popular in South Florida, especially among Hispanics. Although all forms of the sweet potato originated in Central America, the boniato was cultivated as early as 1000 B.C. in Columbia and Peru. A substantial acreage is now planted in Miami-Dade County, Florida. The boniato is often considered a cross between a baking potato and a sweet potato in flavor and color. It is easily distinguished from other sweet potatoes by its pink to burgundy-colored skin and its white or cream-colored flesh. It is also much fluffier, drier, and less sweet than the yellow or orange-fleshed sweet potato.

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Mine were big and difficult to cut so I put them in the microwave for a few minutes to soften them. After cubing the potatoes/yams, I boiled them as usual, to make mashed sweet potatoes. After the microwaving, it only took about 15-20 minutes to boil enough to soften.

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Put the sweet potato in a plastic bag and micro wave for 4-5 min. They are good to eat

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