Dear Cecil: Every now and then I find a green potato chip in with the normal potato chips. Now, I have never seen a green potato (except on Saint Patrick's Day at a diner, the chef of which had a questionable sense of humor, and it was mashed), so I assume that something happens to the chips during the chipping process to inadvertently color certain of their number a virulent verte. Why? Carole F., Alexandria, Virginia

Cecil replies:

Dear Carole:

Green (or brown) chips come from potatoes that have been kept in storage so long that the sugar in them has caramelized. A percentage of taters picked in the fall is stored for use during March through May, when the supply of fresh potatoes is at its lowest. Quality control is supposed to catch the greenies, but some sneak by. I’m told they’re harmless. However, I make no promises.

Oops

Dear Cecil:

After reading your discussion of green potato chips, which you described as harmless, I would like to offer the following comments. When I was a boy back on the family farm in Minnesota, we always raised our own potatoes. Sometimes the potatoes protruded above the ground, and when that happened, the exposed portion turned green as a result of the formation of chlorophyll. We called it “sun scald.” My mother always removed the spots of sun scald when preparing the potatoes for the table because it was common knowledge among farm people that the spots contained a poison, the same as the leaves did.

Potatoes belong to the nightshade family, and most green portions of plants in this family contain an alkaloid poison called solanine. While it is unlikely that anyone has ever become seriously ill from eating the small portions of green sometimes found on potato chips or french fries, some tummy aches could probably have been prevented. They definitely are not good for you!

— Donald L., technical information specialist, U.S. Department of Agriculture, Washington, D.C.

Well, OK. Maybe I shouldn’t have said green potato chips are “harmless.” Maybe I should have said they were “harmless compared to getting hit by a truck,” just to put things in perspective. But let’s get serious. Do you know how many green potato chips you’d have to eat to kill yourself? Fifty kajillion, that’s how many. You could get killed if fifty kajillion potato chips fell on you. So let’s not get too excited here.

Just to clarify: green potatoes result from excessive exposure to light, whether natural or artificial. The green itself is chlorophyll, which is not harmful. However, the same process of photosynthesis that produces chlorophyll also produces compounds called glycoalkaloids, such as solanine, that are toxic in large amounts.

In a normal potato plant, the glycoalkaloids are concentrated in the leaves and the sprouts. The story is told that during World War II some refugees broke into an abandoned house and found a quantity of old sprouted potatoes in the basement. The potatoes themselves were too dried out to eat, so the refugees made a stew out of the sprouts — and got incredibly sick as a result. Thus Mom’s injunction never to eat the eyes in a potato, eyes, of course, being sprouts as yet unborn.

Green potatoes and green potato chips are to be distinguished from brown potato chips, which are a different matter entirely. Brown potato chips result when potatoes are stored too long at low temperatures, causing them to accumulate excessive sugar. When sugar is present in normal amounts, it combines with amino acids during cooking to produce the potato chip’s characteristic yellow-brown color. A chip with too much sugar, on the other hand, takes on a dark brown, almost burned appearance, even though it wasn’t in the oven any longer than usual. This phenomenon is commonly but inaccurately known as “caramelization.” (True caramelization occurs when water is removed from sugar.)

Brown chips are harmless. Green ones won’t kill you in small amounts, but in the words of one authority, “you should not deliberately go around trying to find green potato chips just so you can eat them.” Which pretty much kills THAT party idea. Do the sensible thing and stick to ones you know are safe.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.