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Storing Potatoes

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When potatoes are chilled, an enzyme breaks down the sucrose (aka sugar) they contain and turns it into fructose and glucose, which combines with the amino acid asparagine to form acrylamide, a carcinogenic substance, when heated.

Differences between yams and sweet potatoes are their shape, size and colour, but most people mistakenly refer to them interchangeably. Sweet potatoes are more nutritious than white potatoes, and contain copper/zinc superoxide dismutase and catalase, as well as two antioxidant enzymes; due to the anthocyanins, purple sweet potatoes contain three times the antioxidants.

You can ferment sweet potatoes and purple potatoes as easily as any other vegetable, increasing the nutrition as well as the shelf life.

To most, it would seem as if storing certain veggies in a cool place, such as the garage, back porch or even the refrigerator, would be a good idea. It might keep them cooler and help them last longer, right?

Turns out, that's not how it works with potatoes. When potatoes get chilled, the starch in them turns to sugar and they become tough. They might look OK, but when they're cooked, they may emit harmful properties that they wouldn't have, otherwise. They can become not just slightly shrunken and wrinkled, but potentially toxic.

Here's what happens: When potatoes are chilled, an enzyme known as invertase breaks down the sucrose they contain and turns it into fructose and glucose, also called dextrose, the main sugar manufactured by your body and your chief source of energy.

According to a study published in Risk Analysis, these two sugars, fructose and glucose, combine with the amino acid asparagine in potatoes and form acrylamide when they're baked, fried or otherwise heated.

This doesn't happen with frozen potatoes, however, because sucrose doesn't get broken down by very low temperatures. Acrylamide is made by something called the Maillard reaction, which browns cooked foods and gives them their pleasing flavour.

Sweet potatoes, with their yellow-to-orange-hued flesh, contain two important antioxidant enzymes: copper/zinc superoxide dismutase and catalase. The dark flesh colour also indicates the presence of beta-carotene, another important antioxidant, which is converted by your body to vitamin A to retinol to help protect your eyesight.

But the purple sweet potato variety contains more than three times the antioxidant power due to anthocyanins, also related to their pigmentation, which help fight several types of cancer, including stomach, colon, lung and breast.

Both yams and sweet potatoes are noted as better for you than regular white potatoes, mostly due to the increased antioxidants and fibre content.

But just like white potatoes, they should be stored loosely, not in plastic, but in a dark, dry spot at around 50 to 60 degrees Fahrenheit, but not cold and never refrigerated. Raw sweet potatoes don't freeze well.

The flavour of any potato, whether it's white, purple or sweet, can be adversely affected when they've been stored in cold places.

In their unprocessed form, white potatoes provide nutrients such as vitamin C, copper, B vitamins, potassium, manganese, phosphorus and fibre, along with antioxidant phytonutrients. Potatoes also contain a variety of phytonutrients that have antioxidant activity.

There are lots of ways to prepare both sweet potatoes and purple potatoes. The important thing is to avoid using unhealthy oils and high temperatures in the preparation. That said, you can ferment these veggies as easily as any other to retain optimal vitamins and minerals, and give your body the beneficial microbes it needs. Fermenting vegetables also adds greatly to the amount of time they can be stored.