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What causes potatoes to turn green?

Greening is a natural process for potatoes that have been over exposed to light on the farm, in the supermarket or in home storage. It is not normally found in potatoes that have been grown and stored under proper conditions.

The bitter taste in green potatoes is due to elevated levels of glycoalkaloids (a naturally occurring compound) found in the green skin or in the tissue just under it. Glycoalkaloids are not destroyed by cooking. Any green areas should be cut away and discarded before cooking and eating. If the greening is severe, discard the whole potato.

What causes potatoes to have brown centres or a hole inside?

Hollowheart, a natural defect that cannot always be detected when grading, is a discoloured cavity in the centre of an otherwise healthy potato. It can be caused by rapid growth or possibly by sudden temperature changes early in the growing season. This condition doesn't affect taste or nutritional value, as these potatoes can be eaten, but area around the hollow should be cut out. If you find a hollow centre in your baked potato, simply remove the brown area before serving.

Why do potatoes darken when cooked?

There are two possibilities:

  1. This darkening may be caused by a natural reaction with the iron in the potato. To prevent this, add a little lemon juice or vinegar to the cooking water if boiling.
  2. When potatoes are stored at refrigerator temperatures, the starch in them changes to sugar. When cooked, this sugar "caramelizes' or darkens. Store potatoes at cool, not cold temperatures.

What causes black spots in a potato?

Black spots are usually bruises caused by rough handling. One type of bruising happens when the skin is broken. The potato forms a thicker layer of skin to protect and/or heal the wound. The second type of bruising shows up just under the skin or deeper inside the potato as a black spot. This happens when potatoes are dropped from a hight of more than six inches or when something heavy is placed on top of them. Handle potatoes gently. Store in a cool, dark place. Remove any black spots before cooking.

Why isn't the potato variety printed on the potato bag?

There are no regulations requiring potato variety names to be placed on bags, however, the flesh colour and shape should be shown, i.e. Yellow Flesh Potatoes, Long Type. To help consumers make purchase decisions, many producers now label their bags by variety (see chart listing varieties and uses for a specific cooking method or taste).

Why are potatoes sometimes thought to be high in calories or 'fattening'?

Some people think of potatoes as 'fattening' and consider them taboo on a weight-reducing diet. Nothing could be further from the truth. One medium baked potato only contains about 100 calories. Baked or boiled potatoes are already conveniently portioned, making it easy to control calorie intake. It’s the extras, such as fat added during or after the preparation, that increase the number of calories. As a substitute for popular high-calorie potato toppings, consider these alternatives: yogurt with chives, whipped low-fat cottage cheese blended with lemon juice, grated parmesan cheese, calorie reduced salad dressings, or a mixture of herbs.

Why do French Fries sometimes go dark?

If potatoes are stored at refrigerator temperatures, part of the starch in the potato changes to sugar. The high temperature needed for deep fat frying causes the sugars on the surface of the fries to darken before completely cooking on the inside. Blanching potatoes in hot water 90ºC (170ºF) for several minutes removes most of the sugars and cleanses the surface of the fries to allow them to brown more evenly.

How can I make perfect mashed potatoes?

Some potato varieties are better suited to boiling and mashing than others. For a fluffy mashed potato, choose a Russet variety because of its drier and lighter texture; soggy mashed potatoes could result from over-cooking, i.e. too rapid a boil or too long a cooking time; sticky, gluey, mashed potatoes could be caused by over-whipping.

For perfect results:

  • Choose a Russet variety of potato
  • Add a small amount of water
  • Cook on medium-high just until fork tender
  • Drain well and mash

If, despite your best efforts, your mashed potatoes are too wet, add some instant potato flakes and stir just until combined.