Beer is an ancient beverage. Clay tablets describing the beer brewing process and dating back more than 5,000 years have been found in Mesopotamia. According to these tablets, Sumerians used to prepare “beer bread” out of germinated barley seeds. By crumbling this bread into water, they obtained a liquid called “sikaru”, which was finally boiled and mixed with a few herbs, resulting in a drink free of harmful bacteria.

Over time, different types of starchy plants have been used for brewing,including maize (in South America), soy (in India and Persia), millet and sorghum (in Africa) and rice (in the Far East). Nowadays, beer production using barley malt is the most common brewing process worldwide.

The barley plant is, in fact, a grass. The product of interest for the brewers is the reproductive parts (seeds) of the plant known as grains or kernels displayed on the ears of the plants.

Depending on the species of the barley, the plant will expose one or more kernel per node of the ear. Mainly, two species of barley are used in brewing: the two-row barley (with one grain per node) and the six-row barley (with three grains per node). 

To put it simple, the fewer are the kernels per node, the bigger and richer in starch they are. Conversely, the six-row barley has less starch but higher protein content. Therefore, if the brewer wants to increase the extract content, the two-row barley is the best option, whereas if enzymatic strength is the aim, the six row will be the best choice.

Source Courtesy Mastering Homebrew, The Complete Guide to Brewing Delicious Beer – Randy Mosher

Malt Biology

Barley is a short-season, early maturing crop that is among the most highly adapted grains and can grow in climates ranging from subarctic to subtropical areas. The main risk factors for winter varieties are freezing winter temperatures and over-heating during grain maturation. A temperate climate is ideal for barley. Barley adapts to a wide variety of soils and is, for example,less sensitive than wheat to dryness or poor land.

The planting period runs from mid-September to October for winter barley,while spring barley is generally planted in March to April. Crop density at the time of planting varies from 180 to 200/m², depending on prevailing farming practices and intended use of the crop. The growing season depends a lot on the variety and time of planting. Winter varieties complete their development cycle with a cumulative temperature of 1,900–2,000 °C, while spring varieties need only 1,500–1,700 °C. Harvesting usually takes place from the end of June to mid-July for winter barley and in August for spring barley.

Barley is one member of the family of cereal grains that comprises the majority of the world’s food supply. This family also includes wheat, corn, rice, rye, oats and other grains such as sorghum and millet.

Most of these cereal grains could be “malted,” but barley’s chemical and physical compositions make its malt superior for brewing as it delivers the most desirable flavor characteristics. But not all varieties of barley are considered malting quality, with some only seeing use as cattle feed.

Barley’s enzyme systems — which can quickly convert starches to sugars — render its malt ideal for brewing. Barley also contains the proper balance of starches and proteins, without contributing excessive oils or other undesirable substances.

The rigid husk covering the barley kernel is not easily broken. This protects the kernel throughout harvesting and malting. With all these characteristics, it’s not surprising that over the centuries beer drinkers have come to accept the taste of barley malt beer as the most desirable.

Two Row vs. Six Row

Malting barley can be one of two basic types — two-row or six-row. The names come from the number of barley kernels in each vertical row on the rachis, or plant stem. Predictably, two-row barley has two vertical rows of kernels, and six-row barley has six. Each type has a growth spikelet — a set of three florets — on alternating sides of the stem. For the two-row variety, the center floret forms a kernel, but the outer two members remain sterile. For six-row barley, each floret forms a kernel. As a result, two-row barley kernels typically are plumper and more uniform.

Six-row kernels tend to be slightly smaller, twisted and elongated because they must compete for a limited growth space. The flavor of the varieties differs. Two-row barley produces a smoother, fuller-tasting beer. Six-row barley produces a crisper, snappier flavor.

The embryo, at the base of the kernel, is one of two living tissues in the kernel. The other living tissue, the aleurone layer. During germination, the embryo produces roots and the acrospire which, is allowed to grow, will develop into a new plant. During initial stages of steeping, water enters the grain through the base of the embryo.

The endosperm, which may be thought of as the energy store of the kernel, is the largest tissue in the kernel. It consists of a continuous, highly organized network of cells with walls that contain the highly viscous polysaccharide β –Glucan. Threads of β –Glucan, therefore, are present throughout the endosperm. The cells are filled with starch in the form of discrete bodies, or granules, and rep-resent about 60% of the kernel’s weight. The granules are embedded in a matrix of protein with fairly high levels around the endosperm periphery and relatively low levels in central regions of the endosperm.

Aleurone Layer
Encircling the endosperm, except where it meets the embryo, is the aleurone layer, which is rich in protein and lipids. This layer is three cells thick in barley, but only one cell thick in other cereal grains. These living cells, which synthesize a range of hydrolytic enzymes during germination, play an important role in malting.

Testa, Pericarp and Hull
Outside the aleurone layer and completely surround-ing the kernel are a number of other tissues such as the testa, pericarp and hull. These all play a role in the malting process such as mediating the rate of water uptake during steeping, protecting the embryo during malting and forming the filter bed to clarify malt extracts during brewing. Of particular importance for malting and brewing, however, are the biochemical changes that take place in the embryo, endosperm and aleurone tissues.

Anatomy of a Grain

Acrospire and Rootlets
The last parts are the acrospire and rootlets, which are the germinated parts of the malt. If allowed to grow freely, the rootlets and acrospire would form the beginnings of a rooted barley stalk. However, the malting process arrests this stage through kilning to preserve the starches and enzymes.

Malt Types

Malts are divided into categories by the way they are kilned and how they are used in brewing. The groups proceed from light in color and enzyme-rich to deeply roasted and incapable of any enzyme activity. The terminology of malt can be confusing. There are often different terms for the same malt, and the same name can mean slightly different things in different places. 

Maltsters often have proprietary names for their malts and can be quite secretive about how their malts are produced, making it difficult to compare. The differences between malts can be quite dramatic, and there’s no way you can have any success putting together a recipe until you have a personal sense of what different malts taste like. Get your hands on as many different malts as you can and do what good brewers always do-taste.

Lightly colored malts are collectively known as base malts, because they can form the bulk of a beer recipe, even in the darkest beers. Pilsner, pale, Vienna, mild, and Munich malts fall into this category. Base malts have sufficient enzymes to convert their starches into sugar, while darker malts often do not. Specific base malts are usually associated with either the continental or British brewing traditions. British malts tend to be kilned at lower moisture levels, which makes for more sharply toasty flavors, while continental malts, with higher moisture levels during kilning, display softer, more caramelly notes. English pale ale and German Oktoberfest are both pale amber beers brewed from similarly colored malt, but their malt flavors are very different, mainly due to different moisture levels during kilning. This dichotomy of toasty versus caramelly can be seen from the darker base malts, 5°L, right up to about the 30°L range, where the toasty biscuit/amber malt contrasts with the cookie-like melanoidin malt.

Even malts with moderate amounts of color can still have some enzyme activity. In modem malts, enzyme activity wanes above 25 to 30°L, but in the heyday of porter, malts such as brown and amber were reported to contain enough enzymes to convert themselves.

The next group, a little darker in color and with lower-to-no enzyme activity, is color malt, sometimes known as kilned or high-dried malt. These are created in the same kiln that’s used for drying, but as soon as the moisture level reaches a certain point, the heat is increased and the malt takes on some additional color. The amount of moisture at this stage determines where the malt falls on a spectrum from crisp and toasty to smooth and caramelly. Time and temperature determine the depth of color and the flavors associated with the kilning. Kilning produces malt no darker than about 60 to 70°L.

There is no hard and fast line that separates base from color malts. Munich malt, for example, has sufficient enzymes to convert its own starch to sugar, and so can be used as a base malt in darker beers, but in paler beers may be used mainly for color and complexity.

For darker types, dried malt is sent to a drum roaster, usually a modified coffee roaster. A rotating drum inside keeps the malt moving for uniform roasting. Rapid cooling is essential to stop the color development once a certain target is met. When the machinery to produce black malt was patented in 1819, the key breakthrough was not the roaster itself, but a water spray mechanism that instantly cooled the malt. Roasted malts include chocolate and the various shades of black malt, ranging from 300 to 600°L/600 to l 200°EBC.

There is a gap between mid- and dark-colored malts, between 70 and 200°L. In this gap, flavors are extremely harsh and ashtray-like, not at all suitable for beer brewing (the exception is dark crystal at 120 to 150°L). Above 200°L, the flavors mellow out to various types of roastiness, the unpleasant flavors having quite literally been burnt away.

Caramel or crystal malts are different names for the same family of malt. The processing is very different from other malt types. On the last day of malting, the maltster allows the temperature to rise to 113 to 122°F/45 to 50°C to begin the enzymatic breakdown of proteins and carbohydrates. A unique stewing process, that actually mashes the grain right inside the husk, converts the starches to sugars and gives it a characteristic glassy texture. The maltster “stews” this wet malt to sacchruification temperature, about 150°F/66°C. When much of the starch has converted to sugars, the malt is dried and then kilned to various levels of color. Because there is a lot of simple sugar rather than starch, the caramelization is quite different from regular malts. Crystal malt presents a wide range of caramel, burnt sugar, and raisiny or dried fruit flavors. Each maltster’s caramel/crystal malts are quite different­, an important point when choosing them for your recipes.

Other Specialty Malt Types

This is malt that has been allowed to stew in a Lactobacillus culture before kilning, developing 2 to 4 percent lactic acid, used as a Reinheitsgebot-legal method of acidifying a mash. (Reinheitsgebot is the German beer purity law that limits beer ingredients to malt, water, hops, and yeast.) It is useful as a convenient way of adding acidity to certain styles like Berliner weisse and witbier that traditionally employed lactic fermentations for sour flavors. At 1 percent of the grain bill, acidic flavors will be barely detectable; at 20 percent, the beer will be quite sour. Other parameters of gravity, color, etc., are like Pilsner malt.

This is just a special finishing process in imitation of earlier days when kilns were fired by wood. Beechwood is traditional for the smoked beers of Bamberg, although oak is occasionally used; peat-smoked distiller’s malt from Scotland is not traditional in beer, but can add some scotch whisky aromas. Briess malting makes a cherrywood-smoked malt that has a pungent spiciness.

Unmalted grains have a very long history in beer, but malts have decided advantages: ease of use, readily available extract, and flavor. However, unmalted grains are useful in brewing for mouthfeel, head retention, flavor, or tradition. Ninety percent of the world’s beer is adjunct-based mass-market lager made with corn or rice, which makes the beer easier to drink as well as cuts costs. But even the dreaded rice and corn can be used in creative and interesting ways. And unmalted oats, wheat, rye, and other grains have taste characteristics very different from barley malt, so they’re a good tool to have in your bag of tricks. In amounts up to 10 percent or so, adjunct grains in gelatinized forms like flakes can simply be added to the mash with good results. Brewers have long known that a dab of unmalted grain in a recipe can improve a beer’s head, as the term “head corn” will attest. 

With a few pounds of malt extract in dry or liquid form someone else has already done the hard work of converting malt starches into sugars, often blending in some color, even adding hops for bitterness—essentially instant wort. Because malt extract is a highly concentrated mix of water, sugar, and protein, it has all the elements necessary for a Maillard browning reaction, even at room temperature, which can result in beer with an unpleasant lingering flavor. The term “cidery” is also sometimes used in this context. This browning reaction causes malt extract to darken as it ages, and also during manufacture, so it is often nigh impossible to brew an extremely pale beer, like a German-style Pilsner, with liquid extracts. Spray-dried extracts have a bit better track record for becoming stale and darkening, but they are not immune. Freshness matters.


Maltsters make various measurements of their malt for quality control purposes. When you buy a boxcar load at a time, you get measurements for that particular batch. Those of us who buy in smaller quantities have to settle for more general specifications, of the “not to exceed . . .” variety, which is plenty useful for us. Most malt makers have their specs posted on the Internet, so it’s easy enough to look up whatever you may be using.

Given as a percentage. Lower is better, avoid malts with moisture content of 5% or more, as they have been poorly stored.

Typically given in degrees Lovibond. European malts use European Brewing Convention (EBC) units. EBC = Lovibond × 2.

Extract yield, in percentage by weight, from the malt ground as a brewery would, adjusted to 0% moisture and mashed using the ASBC laboratory mash.

Extract yield, in percentage by weight, from finely ground malt adjusted to 0% moisture and using American Society of Brewing Chemists (ASBC) laboratory mash. The higher the DBFG number, the better.

The difference between the fine grind and coarse grind extract indicates the degree of malt modification. Unless you are using a decoction mash, look for malt with an FG-CG difference of less than 2.0%.

This measures combined alpha and beta amylase, the starch-converting power of the malt. Six-row lager malts have the highest diastatic power, followed by two-row Pilsner, lager, and pale ale malts. Darker kilned malts will have lower diastatic power. Malts above 25°L generally have no diastatic power.

Expressed as a percentage. All-malt beers should not be brewed from malts that exceed 12% protein.

An indicator of the degree of modification. Higher is better for most homebrewing purposes. Malts under 30% are undermodified and may need decoction.

Most malts will be clear to slightly hazy. Highly kilned specialty malts will be noted as dark .

This is about texture, and is another indicator of modification. The more mealy a malt, the better it will mash. Glassy grains do not crush well. Look for malts with at least 92% mealy grains for step mashes or decoctions, and at least 95% mealy grains for single-step infusion mashes.

Malt size is measured by running it through calibrated sieves. The plumper the malt, the better, though uniformity of size is also a factor to look for. Thin or thru means malt that is smaller than 2.2 mm. Look for malt that is 2% or less thin or thru.

This is a measure taken of the wort in a laboratory mash, and is an indicator of glucans or other gummy.

This would indicate any good or bad odors detected in the mash. Most specialty malts will be very aromatic.

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