Test Kitchen recipe: What causes green spot on potato?

Q: What causes the green spot on potatoes?

— Judy Taylor,


A: That can be a common occurrence with potatoes. The green tinge means that the potatoes have been exposed to light exposure or very cold or warm temperatures.

Exposure to light means that they make chlorophyll, which turns them green. When this happens, an alkaloid called solanine — a bitter toxin — develops. solanine when eaten in large quantities can be toxic. You need to cut or scrap any green parts of the potato flesh or skin and discard those pieces. The other parts of the potato are usable.

Because of this, it’s important to store potatoes properly. A cool, not cold, dark and dry place is best. The ideal temperature is in the 45- to 50-degree range. But a pantry is fine, too, as long as it’s not too warm. Don’t store potatoes in the refrigerator, that causes their starches to convert to sugar. And if the potatoes are stored in too warm an area, it causes them to shrivel.

Most sources say not to store onions and potatoes together because both emit gases that cause them to spoil. Also, don’t wash potatoes before storing. This can cause them to decay too soon.

The U.S. produces a lot of potatoes. And it’s no surprise that Idaho is the No. 1 producer of potatoes. But Michigan ranks eighth in the U.S., producing some 1.6 billion pounds, according to the National Potato Council. Nutrition-wise, potatoes are a good source of potassium. A baked potato with skin has more potassium than a banana.

The summer months are a popular time for potatoes, especially with the July 4th holiday. There’s no doubt potato salad will attend many picnics and outdoor cookouts.

There are plenty varieties of potatoes, but some of the best for potato salad are the thinner skin waxy varieties: Yukon golds, new potatoes and red skin. Baking potatoes are a little too mealy for potato salad.

If you’re cooking potatoes for potato salad, I always use this method I picked up years ago while watching the Food Network’s Ina Garten: Slightly undercook the potatoes, and drain them in a colander. Place the colander over a large pot, and cover the colander with a clean kitchen towel. Let them sit for 15 minutes, and the potatoes will steam and continue to cook.

Tarragon-Lemon Potato Salad

Serves: 6

Preparation time: 15 minutes

Total time: 45 minutes (plus chilling time)

2 lbs. new potatoes

1/2 cup chopped celery

1/3 cup chopped fresh Italian parsley

1/2 cup sour cream

3/4 tsp. chopped garlic

3/4 tsp. grated lemon zest

1 tsp. (or more to taste) lemon juice

2 Tbsp. dill pickle relish

1 1/2 tsp. dried tarragon or 4 teaspoons fresh (or to taste)

3/4 tsp. salt

3/4 tsp. freshly ground black pepper

Place the potatoes in a large pot and add enough cold water to cover them. Cover the pot with a lid and bring to a boil. Cook until the potatoes are pierced easily with the tip of a knife, 15 to 20 minutes.

Drain and let cool until you can handle them. When cool, cut them into quarters or halves, depending on the size of the potatoes.

In a large bowl, toss together the potatoes, celery and parsley. In a small bowl, stir together the sour cream, garlic, lemon zest, lemon juice, dill pickle relish, tarragon, salt and black pepper. Pour the dressing over the potatoes and toss to coat. Cover and refrigerate for several hours or overnight.

From “Potato Salad” by Debbie Moose (Wiley, $16.95). Tested by Susan M. Selasky for the Free Press Test Kitchen.

136 calories (13 percent from fat), 2 grams fat (1 gram sat. fat), 23 grams carbohydrates, 5 grams protein, 359 mg sodium, 7 mg cholesterol, 60 mg calcium, 3 grams fiber.

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