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Potato Chemistry in Cooking

Q:

Can you have someone explain the potato chemistry in cooking?

A:

A little bit of knowledge about potato chemistry will go a long way toward understanding why Idaho® potatoes are special, and what contributes to their dry, mealy texture when properly prepared.

Starch is the chief form of carbohydrate stored in plants. The Idaho® Russet Burbank potato is grown and stored under controlled conditions to produce a tuber that has a high quality starch, which is more commonly called solids content.

One of the keys to successful potato cookery is knowing about the starch grains that make up the “meat” of the potato. Each grain is composed of molecules of starch and pectins that chemically are linked together.

During baking, as the molecules are heated and absorb the surrounding moisture in the potato, the grains swell and separate. This process of starch-grain bonding is called gelatinization, and can differ in potato varieties, depending on the size and amount of starch. A potato with small grains such as a round white, will stay firm and waxy, while an Idaho® Russet Burbank with large grains and high starch content, will cook to a characteristically light, fluffy texture. An internal temperature of 208*F. to 211*F. is the test for doneness.

During frying, the same process of gelatinization takes place, dehydrating the surface of the potato and forming a rigid structure that seals each piece. If the potato has a high moisture and low solids content, the fries will become limp if held before serving because of steam captured beneath the sealed surface. For best taste and texture, potatoes should be fried at 350-365*F. maximum.

During microwave cooking, the order of events actually changes. The cooking process takes place by molecular friction… the starch cells rub against each other creating heat. This causes breakdown that can result in a wet, soggy potato.

Traditional boiling methods are generally not effective with Idaho® potatoes. A better method consists of precooking potato chunks to 140*F. water for 20 minutes, then bringing to a full boil and continue cooking until done. It will cause the starch to form a firm gel and prevent separation. This process is called retrogradation and will insure that the Idaho® Russet Burbank can be used in salads, soups and stews without becoming crumbly or disintegrating.

During all methods of cooking, proper handling is essential. If a potato is over cooked or over whipped, the cells will actually separate and gelatinized starches will leak out, resulting in a sticky, gummy potato product.