'nightshade' potato question.

[c0mpl3x]

Tom, with you being in a professional industry that deals directly (both as an individual and as a career) with food, i was hoping you can shed some light on this subject

green on potatoes = poisonous nightshade ?

i was always told this growing up, and to cut it off, but myself i rarely do and have seen nothing bad come from it.



any and all professional answers accepted, i do not want 'well, i heard this/that' replies.

[buceriasdon]

Potatoes and some other plants contain a toxin as a protective mechanism. My understanding is cooking takes care of most of the toxin, but some can remain. Once again you would have to eat alot of green potatoes to become ill. Several pounds worth if I recall.
Don

[c0mpl3x]

Potatoes and some other plants contain a toxin as a protective mechanism. My understanding is cooking takes care of most of the toxin, but some can remain. Once again you would have to eat alot of green potatoes to become ill. Several pounds worth if I recall.
Don

but don, are you implying solid green potatoes, or just the green spots themselves on the pounds of potatoes?

[buceriasdon]

Green under the skins. I remember my German grandmother saying to throw out potatoes with green skins and never understood why until reading about it later in my life. Of course when I was young you never questioned German grandmothers. Ever.

[TXCraig1]

green on potatoes = poisonous nightshade ?

Yes and no, but for safety sake, yes.

Many plants in the genus Solanum including potatoes and as you mentioned, nightshade can produce solanine which is a potent toxin. A couple mg/kg of body weight is enough to make you really sick. An 8oz green potato could easily have several hundred mg of solanine. You would not necessarily have to eat pounds of affected potatoes to get you sick.

The green color on a potato is an indication, but not a guarantee that the toxin is present. The green under the skin is actually chlorophyll (not toxic) that forms as a result of exposure to light. Light also triggers solanine production as a defense against critters eating uprooted potatoes. Most of the solanine forms in and just under the skin which is why trimming them usually takes care of the problem. Baking or boiling a potato with solanine present will NOT denature the toxin.

It is important to realize that either process can happen without the other - a potato can turn green without solanine being produced and vice versa. A bitter taste in the potato is another, and probably more reliable indicator of the toxin being present. If you taste bitterness in a potato, don't eat it. Personally, I throw out green potatoes period. I keep my spuds in the dark, so it is rarely a problem, and they don't cost so much as to make them worth the risk.

CL