North American 2 Row vs 6 Row Malting Barley

by Paul Schwarz and Richard Horsley (Brewing Techniques)

Ever since its introduction to North America in the 17th century, barley has taken on a life of its own.

Both two-row and six-row North American malted barley are rather different from their European cousins and have developed distinctive new characteristics. Genetics, climate, and breeding practices have produced a rich variety of malt qualities from which to choose.

A brewer’s preference for two- or six-row barley can be born of a number of factors, including barley and malt purchase prices, quality specifications, and brewing traditions. Quality of product is in turn affected by genetic makeup, environmental conditions, and the practices of the grower and the maltster.

It is widely believed that two-row barleys are the best barleys for malting and brewing. In fact, outside North America most of the world’s brewing nations exclusively use two-row barley for malt. Six-row barleys, if produced overseas at all, are largely used only for feed.

The situation in North America, however, is rather different and warrants closer examination. Modern American brewing practices have relied on six-row barleys, partly because they were better adapted to many regions. In addition, barley breeding efforts over the past 50 years have reduced, if not obscured, some of the differences between two- and six-row barleys and malts. Yet important distinctions remain in terms of kernel size, extract, protein, and enzyme levels.

The historical preference for two-row barley is based on the fact that two-row barley yields malts with 1–2% greater theoretical extract, meaning that brewers can brew more beer. Largescale brewers, however, must balance the higher extract yield against the higher cost and lower diastatic power of two-row malt. Small-scale brewers with less focus on extract yield may find the differences between the two negligible.

This article delineates some of the principal differences between North American six- and two-row malts in the context of historical developments and current production.

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The Historical Development of Malting Barley Production

Overview: Cultivated barley (Hordeum vulgare) is not native to North America. English, Dutch, and French traders introduced barley to the eastern seaboard during the early years of European settlement. The Spanish introduced it to Mexico and the American Southwest. The imported English two-row barley enjoyed adequate growing conditions on the coast, but as production spread into western New York, six-row barley production dominated because of the climate. The increasing demand fot beer in new midwestern and western cities continued to draw barley producers further west, luring them to agricultural lands more favorable to cereal grain crops. Improvements in the transportation system also helped make this westward shift possible.

North American production trends: United States. As of the mid- to late 1800s, U.S. barley production centered in the area now referred to as the Corn Belt (Iowa, Nebraska, Minnesota, and southern Wisconsin). Disease and competition from corn and soybean crops, however, led to the eventual decline of barley in this region, and U.S. production shifted elsewhere. Today, North Dakota and Minnesota produce the majority of the six-row malting barley in the United States, with lesser amounts produced in South Dakota and Idaho. Two-row barley production predominates in Montana, Idaho, Washington, Colorado, and Wyoming. Both climatic and qualitative differences contribute to the split.

Malting Barley Production in North America

In 1994, growers in the United States produced 375 million bushels of barley. Approximately 50% of production consists of six-row malting types, 12% is two-row malting barley, and the remainder is feed. North Dakota is the largest producer of barley, followed by Montana, Idaho, Minnesota, Washington, and South Dakota, respectively (see map). The United States leads the world in beer production, and most malting barley produced is consumed by the domestic brewing industry. As a consequence, the United States exports little malting barley or malt.

Canada is a major producer of malting barley. With over 9 million acres devoted to barley (30% more than the United States), Canada produced over 536 million bushels in 1994. In contrast with the United States, approximately 50% of total Canadian production is two-row malting barleys, while six-row malting types account for 20%, marking a shift over the past 10 to 15 years from predominantly six-row to two-row malting barleys; the rest is feed. A major reason for this shift is that barley production in Canada greatly exceeds domestic use, resulting in an increased emphasis upon the export of barley and malt — and two-row is the preferred choice around the world. Typically, over 20% of the Canadian crop is exported annually. The United States and China are major customers.

Mexico ranks in the top 10 beer-producing nations, and the national per capita consumption of beer is increasing; however, the domestic supply of malting barley has declined in recent years. Mexico now imports significant amounts of malt and barley from the United States.

Table I: Relative Production, Two-Row vs. Six-Row*
	Grain Yield (bushels/acre)	Test Weight (lb/bushel)	Kernel Plumpness (%)†
Western-grown two-row, irrigated	145	54	89
Western-grown two-row, dryland	90	52	78
Midwestern-grown six-row, dryland	88	47	78
*Typical grain quality parameters for barley produced in the U.S. (Optimal values.) †Percent retained on a 2.4 x 19.0 mm slotted sieve.

Canada. Canada is now a world leader in malting barley cultivation. Production has gradually shifted from the East to the prairie provinces of Saskatchewan, Alberta, and, to a lesser extent, Manitoba. All three provinces grow both two-row and six-row malting barley cultivars, but two-row production dominates Canadian crops.

Mexico. Malting barley production in Mexico is almost exclusively six-row. Most production occurs in the central states, which are generally in close proximity to malt houses.

The box “Malting Barley Production in North America” presents more detailed information on barley production in each country.

Irrigated vs. Dryland Production and Grain Yields

All two- and six-row malting barley varieties produced in Canada and the United States are spring types (Europe grows both spring and winter malting barleys). Seeding takes place in the spring, and harvest occurs from late summer to early fall. Grain yield and hence malt quality are influenced by many factors from seeding through harvest, including variety seeded, environment, diseases and pests, soil fertility, and the agronomic practices of the grower (see Table I).

Irrigation boosts yields in the western United States: The two-row varieties grown in the western United States realize the greatest yield potential, test weight, and kernel plumpness relative to all other barley produced in North America. This advantage comes largely because western barley is more likely to be irrigated by farmers growing under a contract with a maltster. Maltsters pay a premium as an incentive for farmers to grow high-quality malting barley cultivars rather than the better-yielding feed barley. The farmers can thus afford the costly irrigation. Barley not grown under contract is often grown under dryland conditions that limit the plant’s growth potential. High daytime temperatures and/or lack of timely rains during critical periods of crop growth limit the grain yield and kernel plumpness. Irrigation helps mitigate the effects of adverse environmental conditions that can reduce the quality of the grain, thus ensuring a consistent supply of quality two-row malting barley.

Table II: Comparative Analytical Data*
	Two-Row	Six-Row
Extract (% dry basis)	81.0	79.0
Total protein (% dry basis)	11.5	12.5
Soluble protein (% of the malt, dry basis)	5.0	5.5
Soluble total protein (%)	43.5	44.0
Diastatic power (°Lintner)	120	160
α-amylase (dextrinizing units)	50	45
Wort viscosity (cP)	1.5	1.5
Wort β-glucan (ppm)	110	140
Wort color (SRM)	1.6	1.5
*Typical two- and six-row malt quality parameters for barley produced in the United States. Malt quality data represent approximate averages. It must be remembered that considerable variation due to changes in growing conditions, barley quality, or malt processing can occur, even within the same cultivar. Malt quality data are based on the methodology of the American Society of Brewing Chemists.

Barley in dryland conditions: Six-row barley yields in the American Midwest are comparable to dryland yields of two-row barley in the West for many of the same reasons stated above (climate, irrigation). When westetn or European two-row cultivars are grown in the Midwest, they generally yield less and have fewer plump kernels than adapted six-row varieties. This is because the western two-row varieties were developed for areas that may get hot during the day, but that have cool nighttime temperatures that allow the plants to “recover”; the difference between daytime and nighttime temperatures is not as great in the Midwest as it is in the West. The cultivar Triumph developed in Germany, for example, has been successfully produced in the American West.

Disease pressure in the Midwest also limits the yield of many two-row cultivars. On the other hand, midwestern six-row cultivars (with a wider range of adaptation) transplanted to the West have yields comparable to two-row varieties. Consequently, some midwestern varieties are grown under contract in the western United States; the contracting of barley in the Midwest, however, is limited.

The Anatomy of a Barley Spike

The floral structure of the barley plant is the spike, or, as it is sometimes referred to, the head or ear. The spike rests at the tip of each stem, also known as a tiller. Several quality variations between six-and two-row barley are directly attributable to spike morphology, so an understanding of the differences is meaningful.

The central axis of the spike is known as the rachis. The rachis is composed of nodes and internodes, with spikelets that can later develop into kernels attached at the rachis nodes. A barley spikelet comprises an individual floret with surrounding bracts. The barley floret is “perfect,” meaning that it contains both male (stamen) and female (pistil) floral components; barley is self-pollinating. Following pollination, the fertilized ovary develops into the embryo (germ) and endosperm of the kernel, while the bracts form the husk of the mature kernel.

In both two- and six-row barley, each individual node of the rachis has three spikelets, but the fertility (or sterility) of the florets differs in each type. In six-row barley, all three spikelets (per rachis node) contain a fertile floret. These florets develop into kernels and thus each rachis node in the mature spike of six-row barley has three kernels. When the rachis is viewed from one side, there appears to be three rows of kernels. Kernels occur at nodes on both sides of the zigzag rachis, however, so it looks like six rows. This is perhaps most easily seen when viewed downward from the top of the spike. In two-row barley, only the central floret is fertile and will develop into a kernel; the lateral spikelets are sterile, leaving alternating single kernels on opposite sides of the rachis, for a total of two rows. Barley has multiple stems (tillers) per plant, with many of the stems producing spikes. Two-row barley plants generally have more spikes per plant, but the number of tillers is greatly influenced by environmental conditions.

An additional characteristic used to distinguish malting barley types is the color of the aleurone. The aleurone layer is directly under the husk tissues and largely surrounds the endosperm. It is of extreme importance in malting because it is a major site of enzyme synthesis. When certain phenolic pigments are present in the aleurone, they may give the dehusked (pearled) grain a black, violet, purple, blue, or green appearance. It should be noted that these aleurone pigments do not have an easily identified contribution to beer color, but are thought to impact flavor. But again, this impact is not easily quantified.

Absence of pigment results in a white aleurone. Blue aleurone color, which is controlled by a single gene, was once quite common in North American six-row cultivars. In the Canadian grain trade, the blue aleurone trait was once used as a marker to distinguish six-row malting cultivars (blue) from six-row feed cultivars. For the most part, blue aleurone barleys have fallen out of favor with North American brewers, and little blue aleurone is currently produced. All North American two-row barley cultivars have white aleurone.

Canadian barley is grown almost exclusively under dryland conditions, but these conditions are not necessarily equivalent to those of the American Midwest; growing conditions (rainfall, length of season, temperature, and so forth) vary between, and even within, provinces, allowing the growth of both two- and six-row barley. Western Canadian yields are, on average, lower than those for irrigated western U.S. barley.

Only a small amount of Mexican barley is irrigated.

Factors Affecting Barley Quality

Although breeding programs have minimized the differences between two- and six-row barley, differences remain in terms of kernel size/uniformity, grain protein content, and malt enzyme levels. Kernel size and protein directly influence the manner in which six- and two-row barleys are malted by affecting the rate of water uptake, germination, and modification (see Tables I and II).

Kernel size and uniformity: The central kernel of six-row barleys is symmetrical, but the two lateral kernels are slightly twisted and also tend to be slightly shorter and thinner. Two-row barley kernels, by contrast, tend to be symmetrical in shape, more uniform in size, and plumper because only one kernel/rachis node develops (see box, “The Anatomy of a Barley Plant”). Because of the irregularities in kernel size, maltsters often separate each lot of six-row barley into several kernel size fractions for more uniform germination and modification. Plumper fractions are reblended upon completion of malting and used as brewer’s malt. The thinner malt kernels may be sold as distiller’s malt, where it is preferred for its high enzymatic activity. The thinnest barley kernels are removed and sold as feed. Two-row barleys often don’t require such extra handling because their kernel size is more uniform.

A major advance came in 1961 with the release of the six-row cultivar Larker. Larker significantly reduced the size differential between large kernels in six- and two-row cultivars. The name Larker, in fact, was coined from the words “large kernels.” Although this variety is no longer used for malting (having been replaced by newer, improved cultivars), kernel plumpness in six-row cultivars released since that time has generally continued to increase. Nevertheless, the plumpness of two-row cultivars still tends to be greater, particularly when grown under irrigation in adapted environments.

Barley Breeding Programs and Their Innovations

Breeding programs in Canada and the United States have been developing adapted barley cultivars since the early to middle part of this century. All modern midwestern six-row malting barley cultivars can trace their ancestry to barley from northern China (Manchurian types). Manchurian-type barleys gained favor in the northern Great Plains because they suited the regional growing conditions. Two-row malting barleys grown in the West were developed from materials of European origin, where temperatures are somewhat similar to those in the western United States.

The malting and brewing industries take an active role in the development of new malting cultivars in Canada, Mexico, and the United States. The industry offers financial support of breeding programs and research as well as pilot- and plant-scale testing of promising new lines. The industry or their representatives generally make recommendations as to which new cultivars are of acceptable quality for malting and brewing. Several large brewing companies have their own barley breeding programs, but for the most part barley cultivar development takes place at federal- or state-supported institutions. Past goals have focused on domestic markets, but some interest has recently been focused on the development of “export-type” malting barleys and the incorporation of “European” malt quality. Breeding is an ongoing process which requires 8–12 years from the first “cross” to the time of “release.”

Selected cultivars tend to dominate a given region for a few years. After this time they are usually replaced by cultivars with improved quality, higher grain yield, or better resistance to the latest plant disease or pest. Brewers specifications may also change overtime.

The following summaries present current six- and two-row malting barley cultivars in alphabetical order, not in order of recency or volume produced.

Six-Row Cultivars

Azure, released by North Dakota State University in 1982, is the only blue aleurone cultivar recommended for malting in the United States. Many brewers no longer use blue aleurone barleys, and only limited amounts are still produced in North Dakota.

Bonanza, a blue aleurone barley, was released by Agriculture Canada in 1970. It was also produced at one time in the upper Midwestern United States as well as in Canada. Limited acreage remains in the prairie provinces.

Esmeralda, released in 1992 by a national barley improvement program in Mexico, is currently the most common malting cultivar in Mexico. Though Esmeralda’s malt quality is somewhat lower than previous Mexican cultivars, it is tolerant of the disease stripe rust, which destroyed Mexican barley production in the 1980s.

Excel was released by the University of Minnesota in 1990. It has a very high yield potential, but has not gained favor with growers because its kernel plumpness often suffers under environmental stress.

Foster, released by North Dakota State University in 1995, is the most recent barley recommended for malting and brewing in the United States. Foster’s genetic make-up may reduce grain protein levels 1.5% below those of the popular Robust. Foster was named for a former barley breeder at North Dakota State University.

Morex, named for its high extract levels (“more-extract”), was released by the University of Minnesota in 1978. Although Morex’s agronomic quality is somewhat below that of other six-row cultivars, it remains the industry standard in terms of malt quality. Small amounts of Morex are still produced in the Midwestern states and in Idaho.

Robust, released by the University of Minnesota in 1983, is currently the most widely produced six-row malting cultivar. Robust yields better and has greater straw strength and plumper kernels, but lower levels of α-amylase than Morex, from which it was derived.

Stander is a high-yielding cultivar released by the University of Minnesota in 1993 and recommended for malting in 1995. The name Stander is derived from its improved straw-strength (it “stands”). Higher levels of wort-soluble nitrogen and α-amylase are characteristic of this breed. It is the second most widely produced six-row malting cultivar in the Midwest.

Two-Row Cultivars

B1202 was developed by the barley breeding program of Busch Agricultural Resources, Inc. It is largely produced in Montana, Idaho, and Wyoming.

Crest was released by Washington State University in 1992. It is primarily grown for export, and small amounts have been produced in Washington.

Crystal was jointly released by the USDA–ARS and the Idaho Experiment Station in 1989. It is very similar in malt quality to Klages and has shown some resistance to bacterial seed blight, which can be a problem in some irrigated areas. It is primarily produced in Idaho.

Galena (not to be confused with the hop of the same name!) was developed by the barley breeding program of the Coors Brewing Company and was made available to growers in 1991. It was originally intended to replace the German Triumph, but has also replaced some acreage of Moravian III. Idaho and Wyoming produce significant amounts of Galena.

Harrington is the most widely produced two-row malting barley cultivar in North America. It was released by the University of Saskatchewan in 1981 and is characterized by higher levels of enzymatic activity than the previous two-row standard, Klages. Harrington often has poor hull adherence.

Klages was the industry two-row standard before the predominance of Harrington. Very small amounts of Klages continue to be produced, but generally under contract. It was released in 1972 by the USDA–ARS and the Idaho Agricultural Experiment Station.

Manley received registration as a commercial cultivar in Canada in 1990. It is considered to have better agronomic performance, disease resistance, and hull adherence than Harrington and may serve as its eventual replacement. Significant amounts of Manley are produced in Saskatchewan and Manitoba.

Moravian III was released by the barley breeding program of the Coors Brewing Company and has been the predominant barley used by the company in recent years. Moravian III was derived from a cross of Moravian and other European cultivars. The original Moravian was brought to the United States from Czechoslovakia in 1949. Most acreage of Moravian III is in Colorado and Wyoming.

Moravian 14, developed by the barley breeding program of the Coors Brewing Company, was first made available to growers in 1995. It matures earlier than Moravian III, and is thus better suited to some production areas of Colorado.

Oxbow is a new variety developed in Canada that combines Harrington and Manley characteristics.

Kernel plumpness serves as a moderate indicator of malt extract yield. Plumper kernels are thought to have a higher starch content, which is the principal contributor to extract. Before the breeding breakthroughs of the 1970s, the extract from six-row malts was as much as 4% below those of two-row malts. The release of the cultivar Morex (so-named because it has “more extract”) in 1978 marked a trend toward higher extract levels for six-row barley. Currently, six-row malts are only 1–2% lower.

Protein levels: Another important distinction between six-and two-row barley cultivars is in the average level of grain protein. A high protein level often indicates a thinner kernel with less starch available for conversion to malt extract. Acceptable six-row malting barleys may range from 12 to 13.5% protein, whereas two-row cultivars range from 11 to 13%; barleys with greater than 13.5% protein are rarely used for malt. The high temperatures and moisture stress frequently encountered in dryland conditions (under which most six-row barley is grown) can limit the amount of grain fill (starch synthesis) and thus result in higher protein contents.

The protein content differential is also related to genetic differences in how each cultivar accumulates protein during grain development. Total protein content is defined as nitrogen content x 6.25. Because the net loss of nitrogen during malting is minimal, the total protein content does not change greatly in the process. Much of the barley protein, however, is converted into a soluble form by proteolytic enzymes; a portion of this is further broken down into amino acids and peptides in the wort.

Six-row malts tend to yield higher levels of wort-soluble protein. The ratio of soluble protein to total protein is an indication of the extent of protein breakdown (modification) during malting: 40–45% is considered acceptable.

Higher protein malting barleys are generally believed to inversely reduce the level of malt extract in the kernel. In addition, high protein content can lengthen steeping time, cause erratic germination (especially if grain traders blend low- and high-protein barleys to meet protein limits), increase malting losses, and increase enzymatic activity and, ultimately, the level of dimethyl sulfide. High soluble protein levels can sometimes result in brewing or beer-quality problems.

Malt modification time: While most six-row barley cultivars require four-and-a-half to five days of germination to achieve proper malt modification, traditional North American two-row cultivars generally require an additional one to two days of germination time. Harrington, however, a two-row cultivar released in 1981, modifies in only four days. Because Harrington is currently the predominant two-row cultivar in North America, particularly in Canada, it can safely be stated that modern two-row barleys generally require less malting time than six-row barleys — a testimony to the success of modern breeding programs. This advantage represents a major economic consideration for maltsters. This change of tendency for two-row cultivars has represented a major advancement achieved through barley breeding.

Malt enzymes: Six-row malts traditionally (that is, before recent breeding advances) yielded higher levels of the desirable starch-degrading enzymes α-amylases and greater diastatic power (DP). α-amyl