“The king of grains”
June 01, 1995
by Teresa Acklin
Many different wheat classes provide end-use versatility.
For thousands of years, humans have relied on a variety of grains for direct sustenance. In a 1944 book, “Six Thousand Years of Bread,” author H.E. Jacob chronicled how millet, oats, barley, maize and rye each took a turn in the spotlight as a primary food grain over the ages.
But according to Mr. Jacob, one food grain dominated the others and has done so for at least 6,000 years.
“Wheat became the king of grains,” Mr. Jacob wrote. “Since its rise to the throne it has never been deposed.”
Wheat is special, the author said, because it can be baked into raised bread; this is a feat other basic grains, with the notable exception of rye, cannot duplicate. But wheat was discovered before rye. Further, wheat's stature was enhanced over time as wheat-based foods, bread in particular, became intricately woven into a variety of cultures, religions and politics around the world.
Wheat's ability to attain a dominant role in many eras and different cultures reflects its versatility. All wheats belong to the same genus, triticum; but beyond that, the wide variety of wheat classes available has enabled humans to produce wheat-based foods to suit their specific preferences.
In biological terms, all wheats are classified in one of three groups based on whether they have 14, 28 or 42 chromosomes. Durum wheat has 28 chromosomes; all of the other wheats primarily consumed today have 42 chromosomes.
Club wheat and “common” wheat are two species within this last group. In general, common wheat has been categorized further into into eight different types (see adjacent table). These different types are based on three primary criteria: kernel texture (hard or soft), bran color (red or white) and growth pattern (winter or spring).
The classification systems in most major wheat-growing countries are based on these general categories. In addition, the wheats of today's world often are identified in other terms, including geographical location or variety.
Many consumers find this system unfathomable; wheat is wheat, they believe. But a vast range of wheats is available today to suit nearly any purpose; even more important, different wheats are not necessarily interchangeable in terms of their end-use potential.
Whether or not a wheat is suitable for a specific end use is a key component of finished product quality. In general, assessing this functionality depends primarily on a wheat's kernel texture (hardness), gluten strength and protein content.
Hardness or texture refers to the degree of resistance to reduction into small particles. This resistance relates to the force needed to mill the kernel into particles, and the harder the wheat the greater the force required.
Greater forces also cause more physical damage to some kernel components, including starch. Starch damage results in a higher degree of water absorption and in increased gassing power, both of which are prerequisites for high-quality bread flours.
Hardness can be expressed through the Particle Size Index, which is the percentage of fines released after grinding and sifting to distinct specifications. Because soft wheats release more fines than hard wheats, the higher the PSI, the softer the wheat. Figure 1 on page 16 illustrates the relationships between PSI readings, wheat types and origins and end-product functionality.
Wheat gluten strength and dough strength are complementary charactistics. Two widely accepted measurements of this quality aspect are the Farinograph stability reading and the Mixing Tolerance Index. Figure 2 on page 17 shows the functional affiliation between these measurements and various end products.
Wheat protein affects a dough's rubber-like properties, which are required to make leavened bread. Wheat protein content may vary from a low of 6% to nearly 20%; while wheat type plays a major role in protein levels, environmental factors such as location and weather during the growing season also can affect protein from year to year. Figure 3 on page 18 illustrates the relationship between protein content and end uses.
Although wheat is grown all over the world, many countries and regions must import wheat regularly or occasionally to supplement domestic quantities or to obtain higher quality wheat to improve performance. Four countries and the European Union provide most of this imported wheat, together accounting for about 93% of world trade.
Argentina. Argentina produces wheats that are mostly of the hard white spring class; these wheats are planted in late April-May (the fall season in the Southern Hemisphere). Some durum wheat also is planted, but durum area has declined as farmers have switched to higher-yielding spring varieties.
Argentine wheat historically was bought for fill-in stocks by importing millers, but quality gradually has improved. In general, Argentine wheat is considered hard and of medium baking strength.
Argentina uses five grades for common wheat and three for durum. Grades are based on test weight, damaged kernels and foreign material.
Australia. As with Argentina, Australia's location in the Southern Hemisphere means Australian wheat is planted in late April-May.
The country has six classes of milling-quality wheat: prime hard, with a minimum protein of 13%, suitable for high-protein breads, Chinese-style noodles and blending with lower proteins; hard, with minimum protein of 11%, for volume breads and flat breads; standard white, with minimum protein of 9%, for loaf, flat and steamed breads and noodles; noodle, a specific soft wheat variety for white, salted noodles; soft, low-protein wheat for biscuits, cakes and pastries; and durum for pasta.
Australian grading factors include test weight, sprouted wheat, unmillable material, weather-damaged wheat and foreign matter/seeds.
Canada. Canada grows seven types of wheat, including hard, soft, spring and winter classes. Canada also is a major producer of durum.
Hard red spring wheat, which accounts for more than 80% of annual Canadian production, is planted in late April-May (spring in the Northern Hemisphere). The wheat is hard, and mean protein content during the past 55 years has been 13.5%. This wheat is used for breadmaking and for blending with weaker wheats.
The Canadian grading system has been in use since the turn of the century and is an integral part of the Canadian marketing system. Because kernel identification plays a key role in grading, new wheat varieties are licensed strictly to assure they conform to specific kernel characteristics. New varieties also undergo laboratory tests to assess the consistency in milling and baking functionality.
European Union. Of the 34 million tonnes of wheat exported annually from the E.U., more than 50% is French wheat. France markets its wheat primarily on the basis of protein content and physical qualities.
France grows primarily winter wheat, which consists mostly of medium-hard to soft types. Mean protein content generally is 11.8% (dry basis) and typically ranges from 10.5% to 14%.
Available types include high-quality wheats for blending, wheats with high-quality baking characteristics, wheats with variable baking quality and wheats suitable for cakes and biscuits. France also produces durum wheat, with proteins of more than 15% and vitreous kernel counts ranging from 75% to more than 90%.
The United Kingdom also exports wheat, with about two-thirds shipped to other E.U. members. U.K. wheat includes strong bread types as well as biscuit varieties.
United States. The U.S. offers an extremely broad selection of wheat types, classes and qualities. These consist of very hard to soft classes, winters and springs, reds and whites, durum and club wheat. There are six official classes, excluding mixed and unclassed categories, and eight subclasses.
In any given year, soft wheat protein availability ranges from about 7% to higher than 11% (12% moisture basis), while hard wheats range from below 11% to more than 17%. Milling and baking characteristics run the gamut from very mellow to the strongest gluten strength.
Products that can be made from U.S. wheats include cakes, cookies, crackers and noodles of all descriptions; and flat, pan, white, hearth, steam and whole wheat breads. U.S. durum is used for pasta and some selected breads popular in northern Africa.
U.S. grading factors include test weight; defects, consisting of heat or otherwise damaged kernels, foreign material, and shrunken and broken kernels; contrasting classes; other material; and insect-damaged kernels.Typical wheat classes
|Hard red spring (HRS)|
|Soft red spring (SRS)|
|Hard red winter (HRW)|
|Soft red winter (SRW)|
|Hard white spring (HWS)|
|Hard white winter (HWW)|
|Soft white spring (SWS)|
|Soft white winter (SWW)|
|Source: Canadian International Grains Institute|