Why do some potatoes turn black / grey after boiling?

Question

how can this be prevented ?

Answer 1

Purchasing & Storing Potatoes


1 1/4 pounds (3 medium potatoes) equals 3 cups chopped or sliced raw potatoes or 2 to 3 cups cooked mashed potatoes

Potatoes should be smooth, well shaped, and unbruised. When selecting potatoes, choose new potatoes for boiling and salads. They have thinner skins and are firmer.

DID YOU KNOW THAT POTATO SPROUTS ARE POISONOUS? There is no problem with the potato; just cut off the sprouts, and it's fine for eating. A sprout of any size can be toxic, but you'd have to eat many sprouts to get sick. Do not buy if they have sprouted or have a green tint to the skin.

The same is true for potatoes that turn a greenish hue. A potato in this condition is "light-struck." This happens when a chemical, just beneath the potato's skin, reacts to light. The green part will taste a little bitter, but if you peel it off, the rest of the potato will taste fine.

Both conditions can be retarded by storing the potatoes in a cool, very dark place.

Store at room temperature in a dark area. Do not refrigerate.



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Cooking Potatoes
Boiled Potatoes
Boiled potatoes should be started in cold water rather than in hot water. this allows for a more even cooking and heat penetration from outside to inside during the relatively long cooking time required. Potatoes are never COOLED in cold water, unlike most vegetables. This would make them soggy.

Tip: For fluffier boil potatoes, simply pour off all the water after they are boiled and cover the pot with a double thickness of paper towels, then cover with the saucepan lid. In ten minutes, steam will be absorbed by the towels and your potatoes will be dry and fluffy.


Baked Potatoes
Check out my web page on baking the Perfect Baked Potato

Scrub well and pierce the ends with a fork or skewer so steam can escape. Never attempt to bake a mature potato without puncturing the skin - it might explode.

For crisp skins, rub lightly with oil or butter (to prevent skin from cracking and to improve the taste). For more tender skins, leave dry.

Place onto an oven rack in a preheated 400-degree oven and bake until done, approximately one hour. To test doneness, squeeze gently. Done potatoes will yield to gentle pressure.

Aluminum-foil wrapped potatoes are not baked but steamed in their own moisture. The texture of a steamed potato is entirely different from that of a baked potato. Save yourself the trouble and expense of wrapping in aluminum foil and serve a better product.


Mashed Potatoes
Russet potatoes make the best mashed potatoes.

Peel them and cut into equal-sized pieces. Boil and cook the potatoes until they are just tender. Remove from heat and drain. NOTE: Overcooking can cause the potatoes to become gummy.

Dry over low heat for a few minutes. Mash with a old-fashion potato masher or potato ricer (you can use electric mixer, but it is easy to over mix and get a gluey potato). Mash very quickly so the potatoes will remain hot.


Potato Mashers

Potato Ricer



Add one tablespoon butter (more or less if you like) for each two potatoes, and salt to your taste. Beat until the butter is melted. Then add milk or light cream that has been heated but not brought to a boil (if you add cold liquid, the potatoes will be cold and gummy). Beat the liquid into the potatoes to make a smooth, fluffy mixture. Add only enough liquid to make the mixture smooth, about one tablespoon for each potato. Do not overbeat. they should be soft and moist, but firm enough to hold their shape.

All this should be done as quickly as possible so the potatoes never have a chance to get cold - that is the secret of delicious mashed potatoes!



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Learn about the History of Potatoes


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Reasons Potatoes Turn Black After Cooking:

Potatoes occasionally turn gray or dark after they are boiled; this color change may be caused by the conditions under which they were grown or stored. It's impossible to tell which potatoes will turn dark, but the discoloration does not affect flavor, texture, or nutritional value. Contact with aluminum or iron will also discolor potatoes, so cook them in stainless steel pots.

More reasons why cooked potatoes turn black:

1. According to the Idaho Potato Growers at http://www.idahopotato.com/faq/index.php

If the potatoes were stored too cold (below 40 degrees F) then they can turn black. Could also have black bruising from being handled (dropped) when cold.

2. If your potatoes turn black after they are boiled, you may be using an aluminum or reactive pot, so it's important to use a pot that's non-reactive.

3. While cooling, iron in the potato combines with other natural compounds, causing a grey, black, or bluish-purple color. To prevent this, after the potatoes are cooked and drained, stir in a small amount of lemon juice and keep them covered with a tight-fitting lid.

4. According to the American Journal of Potato Research:

After-cooking darkening (ACD) is one of the most widespread, undesirable characteristics of cultivated potato. With the current expansion of the potato-processing industry around the world, there is a renewed interest in the development of new ways to prevent ACD. After-cooking darkening is caused by the oxidation of the ferri-chlorogenic acid in the boiled or fried potatoes. The severity of the darkening is dependent on the ratio of chlorogenic acid to citric acid concentrations in the potato tubers. Higher ratio normally results in darker tubers. The concentration of the chlorogenic and citric acids is genetically controlled and influenced by environmental conditions. This paper outlines the history of ACD and current status of knowledge of the chemistry of the dark pigment formation and its genetic and environmental determinants. Also discussed are the methods of chemical prevention of ACD presently used by the potato-processing industry and potential strategies for reducing tuber after cooking darkening using molecular approaches.

Answer 2

Potatoes will only turn black etc if they are not completly submerged in water when cooking. Alternatively if you peel the potatoes and do not cover in water until ready to cook they will also turn a horrible colour

Answer 3

I've never had that happen after boiling them, but I noticed it will happen if I put them in warm water while I prepare other foods or leave them sit in the air, but not after boiling. Maybe it had a bad spot in it before you boiled it.

Answer 4

They weren't covered with salted water. Use more water next time, and after peeling, but potatoes directly into the water they will be cooked in.

Answer 5

They will only turn black if after you've boiled them, you leave them in water or leave them out.

Answer 6

Are you cooking in an aluminum pot? Try stainless steel.
Are the potatoes being cooked without peeling? They may be rotten on the inside.

Answer 7

If perhaps it's a fruit they have seeds, otherwise it's a vegetable. And vegetables are usually grown in the ground while fruits are grown in trees.

Answer 8

POTATOES CONTAIN STARCH ,BLACKING MEANS OVER OXIDATION TO THE STARCH.SO YOU HAVE TO MAKE LESS TIME WHEN BOILING.

Answer 9

use a clean pan

Answer 10

dead cells