Unbleached flour

Flour is a finely ground meal or powdery product obtained from milling cereal grains, root crops, starchy vegetables, and other foodstuffs.

All-purpose flour is white flour milled from hard wheats or a blend of hard and softwheats. It gives the best results for many kinds of products, including some yeast breads, quick breads, cakes, cookies, pastries and noodles. All-purpose flour is usually enriched and may be bleached or unbleached.

Unbleached all-purpose flour is bleached by oxygen in the air during aging process and is off-white in color. Bleaching will not affect nutrient value.

While bleached all-purpose flour is exposed to chlorine gas or benzoyl peroxide to whiten and brighten flour color.

Carotenoid pigments are present in white flour in extremely low amounts (1 –4 ppm). They provide the creamy, off-white color to unbleached flour.

The advantage of using bleached flour rather than unbleached is that the chemicals used for bleaching act as a preservative so that the flour will not develop an off flavor or spoil after a short period. The chemicals also prevent dough from becoming discolored and provide more consistent results when baking.
Unbleached flour

Gliadin protein in wheat flour

Gliadin is a heterogeneous group of prolamines. They are rather hydrophobic, hence their insolubility in water or salt solutions. They are single chain proteins and such disulfide bonds that occur are all intra-molecular. 

Gliadin is the major storage protein in wheat. Wheat flour has a total protein content of about 10% and approximately 10% of these proteins are made up of alcohol soluble gliadin proteins.

Gliadin is practically as abundant in the wheat kernel. The proportion of gliadin in wheat flour has much to do with its quality for bread making purpose. It is said that gliadin gives tenacity and elasticity to the gluten, while glutenin gives strength; but the two proteins must be present in proper protein of the gluten is to have the properties desired in bread-making.

In order to make a large light loaf of bread, the flour should have a fairly high gluten content and its gluten should contain a high proportion of gliadin.
Gliadin protein in wheat flour

Glutenin in flour

Flour itself does not contain gluten. One of gluten’s main protein fractions in the flour is gliadin which a complex mixture.

At least forty different components may be identified in a single wheat variety. Gluten’s other main protein fraction is glutenin.

Glutenin are protein polymers consisting of high and low molecular weight glutenin subunits HMW-GS and LMW-GS linked though disulphide bonds.

The polymeric glutenin protein have molecular sizes ranging up into the tens of millions of Daltons. The great length of these chains is presumed to confer in wheat its unique dough forming properties.

Glutenin is thought to provide most of the strength also called tenacity, to gluten, while gliadin provides its stretchiness or extensibility. Glutenin also provides elasticity to gluten; that is its ability to bounce back one it is stretched or pressed.

The network of glutenin and gliadin is formed when the long glutenin molecules cross link with hooks on the globular gliadin molecules.

This network is very stretchy and liable, and it appears that the combination of gliadin and glutenin responsible for gas retention in wheat four dough.

The stretchiness lets the dough structure hold on the gas of carbon dioxide, which is produced by yeast or baking powder and form the crumb or texture of the bread.

In cases of gluten intolerance, the gliadin fraction is the cause of the symptoms; the glutenin fraction is not.
Glutenin in flour