Well, since it's happening with different varieties stored under varying conditions, I'd guess you're cooking them in an aluminum pan. If that's the case, try switching to stainless.

Carol

Everything you ever wanted to know (and more!) about potatoes turning black......

***********************************************************
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:

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. 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.

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.

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.

Here is a link that might be useful: Potato Hints and Tips

Wow, interesting question and interesting replies with info.

It had not happened to me so I didn't know it existed. That was very educational. Thanks!

Yes, using an aluminum pot is the usual reason. However, we have hard water around here, iron being the main culprit, so the above mention of iron in the soil/potatoes makes sense. Our water got worse and worse over the years, staining the clothes and shower and such. It was blamed on the shifting water table due to our township building up. A number of years ago I got an ionizer for the water and it cleared up. About 2 years ago our potatoes started turing black when cooked as well as the wash not getting white and it turned out we needed a new ionizer. Do you have city water or a well? If you are not using an aluminum pan and it happens often perhaps you should get your water tested? Happened to our cauliflower too, turned darkish, not black but sort of brown.

This is a big surprise since we have always used the aluminum pressure cooker pot for mashed potatoes and they have never changed color at all--even cut well ahead.

We often whip them and don't want those circular scratches on my SS pots.

Hi, Thanks for the advice. I checked my pots. They are all stamped stainless 18/10. I use bottled water (Poland Spring). My city tap water was tested as safe but tastes awful. I never cook with it. I read about using lemon juice or vinegar. Will try a bit.

I hope I don't need boxed potatoes for Thanksgiving!

My potatoes often turn black after boiling or cooking, but only in the Winter, I surmise that the frost, or cold has damaged them. I never cook with anything other than stainless steel. So it's not the pots that cause this,.I have noticed that any potato with green under the skin, often turns black even after cutting off the green. Complain to the suppliers and maybe they will modify their storage.

Now I do not use any pots, as I steam my potatoes in the microwave in a plastic container. They still turn black , never all if them, but at least 50 % of them. Its nice to know that they wont kill me when eaten, however the colour does put one of enjoying them. I will try the lemon juice method and see if that will work , thanks all for posting .

Mine do as well, and it's my understanding that they've been stored too cold before it gets to the supermarket.

From my experience I find that our garden potatoes that are grown organically do not do this therefore I think that the potatoes that are mass produced turn black because of chemials in the soil. i.e. fertilizers.

I think it's more likely that the grocery store in its ignorance stores their potatoes in as cool room as one store I shop at does. For this reason I don't buy potatoes there.

I took back a bag of potatoes that I bought last week. I baked 4 of them, and 2 of them were gray when I sliced them open.

We usually have enough potatoes from our garden but when I run out I purchase them at the farmers market. For those of you who purchase them from your local grocer add a splash of vinegar in your cooking water. I have been told this works. Let me know. Have a great day.

I have to say that have I never encountered this problem, ever. And I seldom bother to purchase only organically grown potatoes so I seriously doubt it has anything to do with fertilizers or other chemicals. Hard water, possibly; poor storage conditions possibly. Not aluminum pots - I still use my mom's 60+ y.o. aluminum saucepan for cooking boiled pots for salads or mashed. No black potatoes!! But I would be sort of grossed out if they did turn black after cooking :-( I have trouble with blue or purple potatoes as it is.

My sugar is 219 and I gaven’t Eaten yet. What should I eat?