Feb 19, 2014
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FLOUR

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See also Bread, Corn, Oats, Pasta, Potatoes, R ice, Soybeans, Wheat cereals.

Nutritional Profile

Energy value (calories per serving): High

Protein: Moderate

Fat: Low

Saturated fat: Low Cholesterol: None Carbohydrates: High Fiber: Low to high

Sodium: Low (except selfrising flour) Major vitamin contribution: B vitamins Major mineral contribution: Iron

About the Nutrients in This Food

Flour is the primary source of the carbohydrates (starch and fiber) in bread, pasta, and baked goods. All wheat and rye flours also provide some of the food fibers, including pectins, gums, and cellulose. Flour also contains significant amounts of protein but, like other plant foods, its proteins are “incomplete” because they are deficient in the essential amino acid lysine. The fat in the wheat germ is primarily polyunsaturated; flour contains no cholesterol. Flour is a good source of iron and the B vitamins. Iodine and iodophors used to clean the equipment in grain-processing plants may add iodine to the flour.

In 1998, the Food and Drug Administration ordered food manufac- turers to add folates—which protect against birth defects of the spinal cord and against heart disease—to flour, rice, and other grain products. One year later, data from the Framingham Heart Study, which has fol- lowed heart health among residents of a Boston suburb for nearly half a century, showed a dramatic increase in blood levels of folic acid. Before the fortification of foods, 22 percent of the study participants had a folic acid deficiency; after, the number fell to 2 percent.

Whole grain flour, like other grain products, contains phytic acid, an antinutrient that binds calcium, iron, and zinc ions into insoluble com- pounds your body cannot absorb. This has no practical effect so long as your diet includes foods that provide these minerals.

Whole wheat flours. Whole wheat flours use every part of the kernel: the fiber-rich bran with its B vitamins, the starch- and protein-rich endosperm with its iron and B vitamins, and the oily germ with its vitamin E.* Because they contain bran, whole-grain flours have much more fiber than refined white flours. However, some studies suggest that the size of the fiber particles may have some bearing on their ability to absorb moisture and “bulk up” stool and that the fiber particles found in fine-ground whole wheat flours may be too small to have a bulking effect.

Finely ground whole wheat flour is called whole wheat cake flour; coarsely ground whole wheat flour is called graham flour. Cracked wheat is a whole wheat flour that has been cut rather than ground; it has all the nutrients of whole wheat flour, but its processing makes it less likely to yield its starch in cooking. When dried and parboiled, cracked wheat is known as bulgur, a grain used primarily as a cereal, although it can be mixed with other flours and baked. Gluten flour is a low-starch, high-protein product made by drying and grinding hard- wheat flour from which the starch has been removed.

Refined (“white”) flours. Refined flours are paler than whole wheat flours because they do not contain the brown bran and germ. They have less fiber and fat and smaller amounts of vitamins and minerals than whole wheat flours, but enriched refined flours are fortified with B vitamins and iron. Refined flour has no phytic acid.

Some refined flours are bleached with chlorine dioxide to destroy the xanthophylls (carotenoid pigments) that give white flours a natural cream color. Unlike carotene, the carotenoid pigment that is converted to vitamin A in the body, xanthophylls have no vita- min A activity; bleaching does not lower the vitamin A levels in the flour, but it does destroy vitamin E.

There are several kinds of white flours. All-purpose white flour is a mixture of hard and soft wheats, high in protein and rich in gluten.t Cake flour is a finely milled soft-wheat flour; it has less protein than all-purpose flour. Self-rising flour is flour to which baking powder has been added and is very high in sodium. Instant flour is all-purpose flour that has been ground extra-fine so that it will combine quickly with water. Semolina is a pale high-protein, low- gluten flour made from durum wheat and used to make pasta.

Rye flours. Rye flour has less gluten than wheat flour and is less elastic, which is why it makes a denser bread.:j

Like whole wheat flour, dark rye flour (the flour used for pumpernickel bread) contains the bran and the germ of the rye grain; light rye flour (the flour used for ordinary rye bread)

The bran is t he kernel’s hard, brown outer cover, an ext raordinarily rich source of cellulose and lignin.

The endosperm is t he kernel’s pale interior, where t he vitamins abound. The germ, a small part icle in t he interior, is t he part of t he kernel t hat sprouts.

Hard wheat has less starch and more protein t han soft wheat. It makes a heavier, denser dough.

Gluten is t he st icky substance formed when k neading t he dough relaxes t he long-chain molecules in t he proteins gliadin and glutenin so t hat some of t heir intermolecular bonds (bonds bet ween atoms in t he same molecule) break and new int ramolecular bonds (bonds bet ween atoms on different mol- ecules) are formed.

Triticale flour is milled from triticale grain, a rye/wheat hybrid. It has more protein and less gluten than all-purpose wheat flour.

The Most Nutritious Way to Serve This Food

With beans or a “complete” protein food (meat, fish, poultry, eggs, milk, cheese) to provide the essential amino acid lysine, in which wheat and rye flours are deficient.

Diets That May Restrict or Exclude This Food

Low-calcium diet (whole grain and self-rising flours) Low-fiber diet (whole wheat flours)

Low-gluten diet (all wheat and rye flour) Sucrose-free diet

Buying This Food

Look for: Tightly sealed bags or boxes. Flours in torn packages or in open bins are exposed to air and to insect contamination.

Avoid: Stained packages—the liquid that stained the package may have seeped through into the flour.

Storing This Food

Store all flours in air- and moistureproof canisters. Whole wheat flours, which contain the germ and bran of the wheat and are higher in fat than white flours, may become rancid if exposed to air; they should be used within a week after you open the package. If you plan to hold the flour for longer than that, store it in the freezer, tightly wrapped to protect it against air and moisture. You do not have to thaw the flour when you are ready to use it; just measure it out and add it directly to the other ingredients.

Put a bay leaf in the flour canister to help protect against insect infections. Bay leaves are natural insect repellents.

What Happens When You Cook This Food

Protein reactions. The wheat kernel contains several proteins, including gliadin and glute- nin. When you mix flour with water, gliadin and glutenin clump together in a sticky mass.

Kneading the dough relaxes the long gliadin and glutenin molecules, breaking internal bonds between individual atoms in each gliadin and glutenin molecule and allowing the molecules to unfold and form new bonds between atoms in different molecules. The result is a network structure made of a new gliadin-glutenin compound called gluten.

Gluten is very elastic. The gluten network can stretch to accommodate the gas (carbon dioxide) formed when you add yeast to bread dough or heat a cake batter made with baking powder or baking soda (sodium bicarbonate), trapping the gas and making the bread dough or cake batter rise. When you bake the dough or batter, the gluten network hardens and the bread or cake assumes its finished shape.

Starch reactions. Starch consists of molecules of the complex carbohydrates amylose and amylopectin packed into a starch granule. When you heat flour in liquid, the starch gran- ules absorb water molecules, swell, and soften. When the temperature of the liquid reaches approximately 140°F the amylose and amylopectin molecules inside the granules relax and unfold, breaking some of their internal bonds (bonds between atoms on the same molecule) and forming new bonds between atoms on different molecules. The result is a network that traps and holds water molecules. The starch granules then swell, thickening the liquid. If you continue to heat the liquid (or stir it too vigorously), the network will begin to break down, the liquid will leak out of the starch granules, and the sauce will separate.*

Combination reaction. Coating food with flour takes advantage of the starch reaction (absorbing liquids) and the protein reaction (baking a hard, crisp protein crust).

Medical Uses and/or Benefits

A lower risk of some kinds of cancer. In 1998, scientists at Wayne State University in Detroit conducted a meta-analysis of data from more than 30 well-designed animal studies mea- suring the anti-cancer effects of wheat bran, the part of grain with highest amount of the insoluble dietary fibers cellulose and lignin. They found a 32 percent reduction in the risk of colon cancer among animals fed wheat bran; now they plan to conduct a similar meta- analysis of human studies. Whole wheat flours are a good source of wheat bran. NOTE : The amount of fiber per serving listed on a food package label shows the total amount of fiber (insoluble and soluble).

Early in 1999, however, new data from the long-running Nurses Health Study at Brigham Women’s Hospital/Harvard University School of Public Health showed that women who ate a high-fiber diet had a risk of colon cancer similar to that of women who ate a low-fiber diet.

* A mylose is a long, unbranched, spiral molecule; amylopect in is a short, compact, branched molecule.

A mylose has more room for forming bonds to water. Wheat flours, which have a higher rat io of amy- lose to amylopect in, are superior t hickeners.

Because this study contradicts literally hundreds of others conducted over the past 30 years, researchers are awaiting confirming evidence before changing dietary recommendations.

Adverse Effects Associated with This Food

Allergic reactions. According to the Merck Manual, wheat is one of the foods most commonly implicated as a cause of allergic upset stomach, hives, and angioedema (swollen lips and eyes). For more information, see under wheat cer ea ls.

Gluten intolerance (celiac disease). Celiac disease is an intestinal allergic disorder that makes it impossible to digest gluten and gliadin (proteins found in wheat and some other grains). Corn flour, potato flour, rice flour, and soy flour are all gluten- and gliadin-free.

Ergot poisoning. Rye and some kinds of wheat will support ergot, a parasitic fungus related to lysergic acid (LSD). Because commercial flours are routinely checked for ergot contamina- tion, there has not been a major outbreak of ergot poisoning from bread since a 1951 incident in France. Since baking does not destroy ergot toxins, the safest course is to avoid moldy flour altogether.

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