Wheat and Flour Classification

The wide variety of flours available provides a broad spectrum of choice for the baker. Each flour has its own inherent characteristics, predisposing it to produce certain attributes in the loaf after baking. Flavor, aroma, color, volume, crust and crumb texture are all largely affected by the baker's choice of flour.

Wheat, in the cereal group of the plant family Gramineae, exists in various species. Over 90% of wheat production in North America is Triticua aestivum (T. vulgare), because its flour is particularly suited to the production of leavened bread. Over 100 varieties make up the species, with new ones constantly being developed, but only a small fraction is commonly cultivated for bread baking flour. In many growing areas, the suitability of cultivating either of several varieties overlaps. The same variety can also produce different results depending upon where it is grown. The characteristics of the grain vary crop by crop depending on soil, climate and other environmental conditions during the growing season. In addition, the various types are usually mixed and marketed together. Thus, classification by specific variety is not useful.

A common classification is into Spring or Winter classes, and Hard or Soft varieties. Color, either red or white, is often noted, but is not an essential factor in the discussion. (Most wheats used in bread making are red, although white wheats are increasingly being promoted.)

Winter wheats are planted and geminate in the fall, lie dormant during the mild winter, then resume an active growth in the spring, to be harvested in early summer. Spring wheats, grown in severe winter areas, are planted in the spring and harvested in late summer.

Classification as either hard or soft describes the protein in the wheat and correlates to its suitability for various baked products. The protein in soft wheats is well suited to produce the tenderness and texture desired in cakes, cookies, crackers, ice cream cones, cake donuts, etc. Hard wheats contain greater quantities of glutenin and gliadine, the gluten-forming components of moistened, kneaded flour. This protein-based structure is uniquely suited to form a membrane that retains the gases produced during the fermentation of the dough, giving bread its desired crumb structure with large, open holes, or alveolus. It produces a chewier texture.

Lastly, and in this country, most importantly, flour are specified by the quantity of its protein. This ranges from six to 18% and depends upon the variety as well as the climatic conditions during growth. In general, the flours highest in protein are milled from hard spring wheats.

After the quantity of protein in the wheat has been determined, laboratory tests attempt to establish the suitability of that flour for bread making purposes. The standard benchmark instrument used in the United States is the Farinograph, which determines absorption and mixing parameters. Ash and enzyme content are also established. Almost all flour sold in this country is classified upon these test results. Millers, from whom artisan bakers buy mostly bagged, brand name flour, use these criteria to set standards and to attempt to maintain consistency within each of the many brand names offered.

Of infinitely more importance to the baker than wheat variety or the amount of protein it contains, is the quality of its protein. Here, quality is described in its rheological sense: how it can be expected to behave during mixing, kneading, fermentation, shaping and baking. These rheological characteristics deal with the dough's plastic qualities: its elasticity, its extensibility and its tolerance. They tell the baker if the dough will stretch to the full length of a baguette, if it will retain it fermentative gases, if it will produce the texture and hole structure sought, if it will spring to a beautiful volume in the oven. These characteristics can be predicted I the laboratory, to a high degree of precision by the Chopin Alveograph, a standard piece of test equipment in Europe, but little used in the United States.

The true test of the baking quality of any flour is in actual baking. In this country, all laboratory test baking is conducted using small loaf, or "pup" pans. Test results are measured almost exclusively in terms of loaf volume, and any examination of interior texture is made in comparison with the even, small hole structure desired by industrial, American bread bakers. Taste, considered too subjective for scientific analysis, is never judged.

For hearth breads, a flour is needed that will produce a loaf with the desired flavor, volume and texture, without depending on the support of a pan during long fermentation, final proofing and baking. "High" protein flours, at levels of 14% or above, are often recommended by suppliers for these breads, because they are capable of stretching. However, the dough they produce can be "bucky", and therefore not support a long fermentation, crucial for maximum flavor. These super high protein flours also tend to "tear": the structure of their protein membrane becomes porous. They can also yield a tough texture in both crumb and crust. Many bakers are looking for a flour with a balance among its plastic characteristics producing maximum volume, a crumb texture which is well alveolated, an interesting mouth feel, or "chew", and a crisp, yet tender crust. These results can often be achieved with flours marketed with protein levels of approximately 12%.

In conclusion, a classification system is useful only if it helps in making choices. The American classification system for flour is based primarily upon the measurement of protein quantity, and secondarily quality parameters quite different from those of concern to artisan bakers. Professional bakers must develop their own specific performance and quality characteristics, and make careful flour choices from within the established classification system.

© By Danielle Forestier, this, in a slightly modified version, was originally published in the Bread Bakers Guild of America Newsletter, September, 1993. Since the original publication of this article, it has become more common to obtain alveograph results from the millers, some now providing it routinely.