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Malting grain

Picture of Malting grain

Malt and grain look very similar, but before grain becomes malt, it goes through a relatively complex process - malting. The grain of barley, by far the most important grain in brewing, consists of over 60% starch and long-chain dextrins, but only about 2% sugar. Even with other brewing grains such as wheat or rye, the approach is not fundamentally different.

Yeast cannot process starch, it only ferments sugar. The breakdown of starch into fermentable sugar happens during mashing, but malting creates the conditions for fermenation. The endosperm of the grain is the iron ration of the grain. In it, energy and the building materials are stored in an efficient way. This energy is what the grain needs for germination at the beginning of its growth cycle, and is also exactly what the brewer needs for the creation of alcohol. In order to make them available the breakdown of the grain content begins with germination.

Enzymes are the boosters of this breakdown. They are biological catalysts that accelerate biochemical processes without changing themselves. Most enzymes are already present in small quantities in barley, but are activated and multiplied during germination. One of the most important enzymes, the starch-degrading α-Amylase is entirely produced in the aleurone layer during malting.

The malt obtained in the end is either diastatic, that is to say has enzymatic power, or non-diastatic. Diastatic malts contain natural enzymes that break down starch into sugar. The more a malt is kilned at high temperature, the less enzymes it contains and therefore its diastatic power is lower or even zero for roasted beans. It is therefore necessary to brew non-diastatic malts with diastatic varieties so that the starch can be converted into fermentable sugars. Pale malt or pilsner contains enough enzymes to convert its own starch and the same amount of non-diastatic malt or unmalted grain. This principle is what makes the Irish Pot Still whiskey style possible.

Water activates the grain

The grain is treated alternately with and without water within a drainable steep for 2-3 days. The time under water takes up about 1/4 of the total time. In between, the grain is supplied pneumaticly with air to start germination. At the end of the steeping phase of production the barley will reach a moisture ratio of between 40-45%.

The water must be clean, soft and not too cold, ideal water temperature is between 10°C and 13°C. Colder water leads to longer soaking times whereas warmer water provokes stormy germination. To ensure better cleaning of the grain and leaching of tannins from the husks, alkalis (CaO (quicklime), NaOH (Sodium hydroxide, also known as lye or caustic soda) or Na2CO3 (Sodium carbonate)) can be added to the first steep.

Steeping or hydration process

The Steeping process is designed to evenly hydrate the endosperm mass to a moisture content of approximately 40-45% ensuring uniform growth during germination. There are a wide variety of hydration processes that can be used depending on the technological conditions of the malt house and total Steeping times can vary from as little as 24 hours to 72 hours or more. Aeration and C02 extraction is also normally carried out during steeping.

The widespread wet steeping method is done by immersing the grain in water. This process consists of three wet steeping of 2–4 hours, during which the soft material is ventilated every hour. In the approximately 20-hour air gap in between, the CO2 is extracted every hour at the beginning and later continuously.

The flood steeping process consists of two 6-hour steepings, with the grain being flooded with water twice for 5 minutes in the 40-hour air gap in between in order to secure the water supply and to control the temperature.

With the spray steeping process, the water is sprayed directly onto the grain in the germination box, which means that no additional germination systems are required. It is sprayed twice for 6 hours each from nozzles on the turning trolley or drum. Each spraying is followed by an 18-hour air blast. Before germinating, it is sprayed again for 1/2 hour. The grain is turned slowly several times to ensure good water distribution. At the end of the hydration process, the grain should be swollen and elastic and it should be possible to bend it over the fingernail. It should be possible to squeeze it between your thumb and forefinger without resistance to produce a characteristic click.


Once hydrated the grain is malted during which time cooled, humidified air is blown through the grain to maintain the moisture and the grain is turned to prevent the roots from tangling. Traditionally malting was conducted on floor maltings, though this has largely been discontinued as this method is labour intensive and lower yeilding than other methods. A number of distilleries historically operated drum maltings and Saladin boxes though these have largely ceased as well with commercial malting plants now supplying most distilleries.

During the Germination period they barley will start to germinate and produce enzymes such as amylase. This stage lasts from four to six days, variable depending on the barley, and gives rise to what is called green malt. Amylase, an enzyme found in barley cells, converts starch into sugars and proteins into amino acids. About 5% of the starch in barley will be converted into sugars, but the enzymes necessary for this process could only develop during germination. There is another important chemical reaction that takes place in germination and that is the liquefaction of cell walls. The cells in barley seed lose their cell walls by the combined action of several enzymes: cytase, xylanase and pectases. The starch is transformed into a kind of whitish flexible flour from which the sugars will be extracted during the brewing. The heat generated by the growth requires regular turning of the barley to prevent the rots from tangling. When these sprouts have reached a length of two to three millimeters, germination is interrupted in order to prevent the the consumption of the grain sugars.

Factors influencing germination

Temperature, oxygen and water content control the germination process. When germinating, the grain exhales glucose and oxygen and forms carbon dioxide, water and heat according to the Stoichiometric Equation : C6H12O6 + 6O2 ⇒ 6CO2 + 6H2O + 2822kJ

The oxygen content must be regulated in such a way that germination does not occur unevenly and and that respiration does not come to a standstill killing the germinating grain. For the same reason, the water content in the grain must always be kept above 40%.

On floor maltings the resulting heat must be dissipated through pile management and ventilation though most modern solutions automate this. The exact temperature profile depends on the type of grain being malted and the variety specification. Germination starts at around 10°C then the temperature is allowed to slowly rise. With light malts, it reaches around 18°C from the 6th day. Darker malts are dissolved more strongly by letting the temperature rise to around 25°C on the 5th and 6th day.

The root germs are already visible on the 2nd day of germination. On the 3rd day they fork. By the 8th day of germination, they grow to 1.5 times the length of the grain for light malt and about twice the grain length for dark malt.

In addition, the leaf germ develops, which by the end of germination reaches a length of 2/3 to 3/4 of the length of the grain for light malt or 3/4 to full grain length for dark malt. In barley it can only be seen as a small bulge under the husk. If it grows further over the Kornspitze and becomes visible there, one speaks of “hussars”, which indicate overdissolved malt.

In addition to the formation of enzymes, a number of other processes also take place inside the grain. The cell walls of the starch cells are partially dissolved. Part of the starch is broken down into sugar with the help of the enzymes, so that the starch content drops from approx. 63% to approx. 58%, while the sugar content increases from approx. 2% to approx. 8%. The protein in the grain is also partially broken down in order to generate new cell tissue such as the root germs from it.

Kiln stops germination

Once the grain has dissolved far enough, germination is stopped by dehydration during kilning. The water content drops from over 40% to below 5%. For this, dry, warm air is blown through the malt. To protect the enzymes, the temperature must first be kept below 50 ° C until the water content of the malt has fallen below 20%. Only then can the temperature be increased further.

Light malts such as Pilsner malt are first kilned to a water content of 10–12% at 40–50 ° C and vigorously ventilated. This ensures that the enzyme activity comes to a standstill through rapid dehydration and thus prevents the excessive formation of sugar. After that, it is only heated to 80 to 85 ° C. This ensures the light color and the typical pure, grainy, sweet taste with only a very low maltiness.

With dark malts such as Munich malt, value is placed on darker color and malt aromas, which are brought in by melanoidins. They are created when sugar and amino acids are converted at relatively high temperatures. Drying takes place slowly, with little ventilation and only up to a water content of around 20% at 40–50 ° C. The enzymes can work longer and produce a higher proportion of sugar than with Pilsner malt. Then it is heated up to about 105 ° C in order to form the melanoidins and the typical malty taste.

Specialty malts

Special malts add color and different aromas to beer. They are made with very different processes; in particular the kiln process differs considerably.

Colored or roasted malts

These malts are primarily strong coloring, but also bring a roasted taste. Roasted malts that have been hardened to a very high level and have not been peeled can also taste bitter and burnt when given in large quantities. Peeled roasted malt, from which the husks are removed before roasting, has a milder taste.

Colored malt is produced by roasting green malt or remoistened kiln malt at temperatures of 180 to 220 ° C. The malt is constantly moved in a drum or ball and regularly moistened to reduce the bitterness.

Brewed or melanoidin malt

This malt has a medium color and is very aromatic due to its high melanoid content. It has a high content of protein breakdown products.

Melanoidin malt is created when the temperature during germination is allowed to rise to around 50 ° C after a few days, either by contracting and leaving the pile or by adding warm water to the germination box. This ensures a strong enzyme activity and the formation of maltose and amino acids. The malt is kilned at 90–100 ° C. Many melanoidins are formed in the process.

Caramel malts

Caramel malts are produced in many color gradations. Accordingly, they color differently and ensure full-bodiedness and good foam properties.

Common to all caramel malts is the saccharification of the green malt in a roasting drum at around 70 ° C. Then it is kilned at different temperatures: very light caramel malt from around 80 ° C, dark from around 150 ° C.

English, Belgian and American caramel malts are also offered in many other color grades, with which the kiln temperature and duration vary accordingly.

Pointed malt

Pointed malt is a malt that has only germinated for a short time and is therefore not very well dissolved. As a result, it contains, among other things, many higher molecular weight proteins that ensure good foam stability in beer. In contrast to raw fruit, which would have almost the same effect, pointed malt complies with the German purity law.

Sour malt

Sour malt is light malt on the surface of which lactic acid bacteria have been cultivated. These are killed by kilning, but a lactic acid content of 1–2% remains. This allows the hardness or residual alkalinity of the brewing water to be reduced without violating the purity law.


After kilning, the root germs are separated from the malt when cleaning the malt. This takes place in a slotted drum in which the root germs are knocked off the malt grain by a beater shaft. The germs, which make up about 3–4% of the total amount, are used as animal feed.

However, the malt is still not ready for use, because freshly kilned malt leads to lautering and fermentation problems in the brewery. It must be stored for at least 4 weeks, with physical and chemical changes in the malt body making it easier to work with. The water content increases again slightly to 4-5%.

Finally, the malt is again cleaned of dust and loose husks. This process is called polishing. In the polishing machine, coarse parts are first separated through a sieve, then the malt grains are brushed to remove dust.

A total of 100kg of grain turns into about 78kg of malt. If the different water contents of grain and malt are taken into account, the dry waste is around 10–13%. It is mainly caused by breathing during germination and the separation of the root germs, and to a lesser extent also by losses during steeping and polishing.

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