I recently purchased a bag of russet potatoes and every one I cut into had turned green. This wasn’t just under the skin, but all through the potatoes. I don’t plan to cook these but I wonder if they are unsafe. — Kay P.
A. Hi Kay. No, you don’t want to eat any potato with that much green in it. The green color generally indicates the formation of chlorophyll, which is natural in plants. But, when it show up in a tuber, as it does in potatoes that have been exposed to enough light, it indicates the presence of glycoalkaloids, especially solanine. Ingesting solanine can make you very ill. Not as serious, but still undesirable, is the fact that solanine also gives cooked potatoes a bitter taste.
If this was a matter of just a shallow layer of green under the potato skin, you could just remove it before cooking. But, since the color is throughout the potato, I’d suggest taking the whole bag back to the store. Get your money back and alert them to what might be a potential problem for other customers.