Loud and clear, malt is nothing more than cereal grains that have gone through the malting process. This process, broadly speaking, is based on the controlled germination of the grains and their subsequent drying/baking. Malting activates diastatic enzymes, which are then responsible for converting grain starches into fermentable sugars. Also, the process gives the grains the characteristic color and aroma that later contribute to the final character of the beer.
For the malting process, only the highest quality grains are selected. This selection depends, among other things, on high starch content, uniform grain size, low nitrogen content and high diastatic power. This last term refers to the ability of grains to break down complex starch molecules into simple sugars to make beer, and depends on the amount of diastatic enzymes contained in the grain.
Barley is the most common malted grain, but there are other grains that are also malted, such as wheat or rye. Due to differences in processes, malts of similar types from different malthouses can impart different flavors to the beer. Brewers usually select their malts from specific malthouses, with which they already know that they will achieve the desired result.
Besides beer production, malted grain has many other functionalities. It is used, for example, in the production of whiskey, malt vinegar or Whoppers candies.
The malting process:
Malting consists of three phases:
Soaking and germination: The malting process begins when the grains are soaked for 38 to 46 hours, until they have absorbed at least 50% of their initial weight in water. They are then drained and transferred to the germination room, where they reside for almost four days with constant humidity and temperature. The grains have to be removed periodically so that they maintain a temperature between 15 and 24ºC, which favors germination.
The germination process, for its part, takes advantage of the natural growth cycle of the plant, activating the enzymes present in the grain. These enzymes begin the process of breaking down the proteins and starches lodged in the center of the grain. The moment at which this decomposition takes place is called modification. Most brewing malt produced today is highly modified, which translates into a significant amount of enzyme development.
Drying: Once the maltster determines that the grain, now called green malt, has been sufficiently modified, it is moved to the kiln and carefully dried to around 4% moisture. Drying lasts between 24 and 36 hours, at a temperature between 50 and 70ºC. For some types of malt, the process ends here. These malts are called base malts.
Baking: After the beans are dried, they are heated in ovens at high temperatures and for long periods of time. This long process gives the malts their unique colors and flavors. In general, low temperatures and short bakes tend to result in light-colored beans with somewhat subtle flavors. Instead, longer kilns and higher temperatures give rise to dark malts, with much more intense flavors.
In this development of colors and flavors, two chemical reactions are involved: caramelization and the Maillard reaction. On the one hand, caramelization refers to the decomposition of sugar at high temperatures, which gives rise to sweet flavors such as toffee, molasses and raisins. The Maillard reaction (named after the scientist who discovered it), on the other hand, refers to the darkness that occurs due to the interactions of amino acids with sugars. It is, in fact, the same reaction that occurs when you toast bread or make those funny marks on grilled meat. When the Maillard reaction occurs, we find bread, toast and cookie flavors, associated with the typical aroma of baked biscuits. Malts that have been kilned or roasted are called specialty malts.
Types of malt:
Malts can be divided into three categories, depending on the duration, temperature, and moisture level during kilning. These three types are as follows:
They are the lightest of all the malts used for brewing, due to low temperatures and short kilning times. While high-temperature kilning breaks down grain starches and depletes diastatic enzymes, lower-temperature kilning allows base malts to retain most of their potential sugars, as well as contain the highest diastatic power of all malts. In short, base malts contain large amounts of fermentable sugars, while they are capable of transforming not only their own starches, but also those of those malts with less diastatic power. For this reason, base malts are used in any recipe and in large quantities (normally at least 85% of the malts in a beer are base).
Due to the high enzyme content of these grains, base malts always come from barley or wheat. Some of the best known are the Pilsner, the Pale Ale, the Munich or the Vienna. The latter two are baked at slightly higher temperatures (for a more roasted flavor and dark color). However, these four malts, and all base malts in general, are characterized by bringing a mild, grainy sweetness to the beer. Some styles that traditionally only contain base malts are the Pilsner, the Munich Dunkel and the Cream Ale.
These malts are also called Cristal (according to the English). The Americans, however, call them Caramel. To create Caramel malts, the green malt is not dried, but goes directly to a roaster at the end of germination. In this roaster, the beans are heated to a temperature of 65-70ºC, in order to activate the diastatic enzymes. These enzymes, in turn, transform the starches into sugars contained in the center of the grain, in a semi-liquid state. Subsequently, the beans are roasted at temperatures between 100 and 160ºC, depending on the desired color and flavor. However, this process causes both the caramelization of the sugars to forms that are not as easily fermentable, and the darkening of the grains due to the Maillard reaction.
Among the Cristal malts, the darker ones give the beer flavors of toffee, burnt sugar, and raisins, while the slightly lighter ones give the beer reminiscent of honey and caramel.
Malt color is measured in Lovibond degrees, a name that comes from the inventor of this measurement method, originally created to measure the color of beer. According to this method, lower numbers refer to lighter malts, while higher numbers designate darker malts. In general, Caramel malts are usually between 10 and 120º L, although some can reach 150º L.
We can find these malts in styles such as the American Amber Ale, the English Bitter or the Scottish Ale.
Roasted/roasted malts. Roasted malts are made by baking completely dry base malts at temperatures above 170ºC. The higher the temperature, the more the Maillard reaction increases to the detriment of caramelization, giving the beans medium to full dark colors, with flavors reminiscent of the same toast, walnut or cookie. Some examples of this type of malt are Brown, Amber or Aromatic, and are used to make beers such as Brown Ales. Likewise, they are also used to define the character of Bock and American Pale Ales.
And what about Stouts and Porters? To make this type of beers, there are totally dark malts, with very powerful flavors, which provide the black color and the roasted flavor. To obtain these malts, the green malt is first dried in the oven at a temperature of around 70ºC and with low humidity levels. Once the grains are dried, the temperature is raised little by little to between 215 and 250ºC. Although this process does cause some caramelization, most of the color and flavor comes from the Maillard reaction. At that temperature, in fact, the grains can even catch fire. To avoid this, they are subtly sprinkled with water. These temperatures offer the malt an intense flavor of chocolate, coffee or roasted. In addition, due to its intensity, a low percentage is usually used when making beer (between 3 and 5%). In Stouts, however, higher amounts can be used. Otherwise, lower amounts are also used if you want to give the beer a darker color, with little influence on the taste. Apart from Stouts and Porters, we can also find small amounts of roasted malts in Scottish Ales and Brown Ales.
What grains are malted?
By far, barley is the most widely used grain in brewing, and the fifth most widely grown cereal in the world. It is also one of the oldest, as it was already cultivated more than 8 thousand years ago.
Barley is grown mainly in the colder temperate climate regions, such as Russia, Canada, Spain or Germany. There are three types: two-row malt, four-row malt, and six-row malt. This fact refers to the number of grain rows of each stem. Of the three, only the two-row and six-row barley is used for brewing, although the two-row is the most popular. Some of the best known barley varieties for brewing are Harrington, English Marris Otter or Halcyon.
Of all the types of cereal, it is no coincidence that barley is the most widely used. Barley is characterized by short germination and high starch content (thus facilitating a higher amount of fermentable sugars). In addition, this cereal contains a high protein concentration, a fact that reduces the cloudiness of the beer.
Although most barley is malted for later brewing, it can also be used raw or unmalted.
Other types of malt
Apart from barley, we brewers also often use wheat, rye or oat malt. Among the many uses that these malts can have, we can enhance the body of the beer and facilitate the formation and retention of foam. Likewise, they also contribute to creating a more complex beer, with a unique flavor.