A pale lager and a stout may both begin with barley. Yet one can smell of fresh bread and light honey, while the other brings coffee, dark chocolate and burnt toast.
Many of these differences start in the malt house, before the grain reaches the brewery.
Malt is grain that has been allowed to begin germinating, then dried to stop its growth. It provides the starch that will eventually become fermentable sugar, but the type of grain and the way it is malted also help shape the beer’s colour, aroma, body and flavour.
Preparing barley for brewing
Barley is the most widely used brewing grain because several useful features come together inside it.
The endosperm contains starch, stored as energy for the young plant. The embryo is the part that will begin to grow when the grain takes up water, while the tough outer husk protects everything inside. That husk also becomes useful in the brewery, where it can help form a natural filter bed as the brewer separates the sweet wort from the spent grain.
Barley contains enzymes too. During brewing, these help break the starch into sugars that yeast can ferment. Its proteins provide nutrients for yeast and can influence foam, body and haze in the finished beer.
In raw barley, however, the starch is difficult to reach. It sits inside the endosperm, surrounded by cell walls and proteins. Malting begins to break down those barriers.
The process usually takes place in a maltings or malt house under the supervision of a maltster. Most breweries buy malt from specialist producers, although some have malting facilities of their own.
It begins with steeping. The barley is immersed in water during a wet stand, then drained and exposed to cool air during an air rest. These stages are normally repeated two or three times until the grain has absorbed enough water to begin growing.
Once hydrated, the barley reacts as though it has been planted.
The embryo begins to develop and its first root tip, known as the chit, emerges. Inside the grain, enzymes become active and the structures surrounding the starch begin to break down. The barley is turned regularly to keep the temperature even and prevent the growing rootlets from becoming tangled.
At this stage, it is known as green malt.
The maltster has to stop its growth at the right moment. Left for too long, the young plant would begin consuming the starch and nutrients the brewer needs. Stopping too early would leave the grain insufficiently modified and the starch harder to access.
Warm, dry air is passed through the green malt during kilning. This stops germination, lowers the moisture content and makes the malt stable enough to store and transport.
Kilning also begins to shape how the malt will smell and taste.
What heat does to malt
Gently kilned malt can retain a pale colour and aromas of fresh grain, bread dough or crackers. As the temperature rises, those aromas can deepen into bread crust, biscuits, toast and nuts.
The maltster must balance this flavour development with enzyme activity. Lower kilning temperatures preserve more of the enzymes needed during mashing. Higher temperatures create deeper colour and stronger aromas, but gradually destroy those enzymes.
Many of these colours and aromas develop through the Maillard reaction, the same family of reactions that helps form the browned crust on bread. In malt, reactions between sugars and amino compounds can produce characters ranging from biscuit and toast to coffee and chocolate.
Caramelisation involves sugars alone. It can create flavours such as caramel, toffee and black treacle when the grain is exposed to more intense heat.
By changing the moisture, temperature and time used during kilning or roasting, maltsters can take the same raw material in very different directions.
Pale base malts sit towards one end of that spectrum. They are kilned at relatively low temperatures, preserving the enzymes needed to convert starch during brewing. They also supply most of the starch, proteins and nutrients in a typical beer recipe.
Pilsner malt and pale ale malt are common examples. Depending on the malt, they may bring aromas of fresh grain, bread dough, crackers or light honey, along with a straw or golden colour.
Pilsner malt is particularly lightly kilned. This helps preserve its pale colour, but can also leave higher levels of compounds that may lead to dimethyl sulphide, or DMS, during brewing. DMS has an aroma often compared with cooked sweetcorn. A vigorous boil helps the volatile compound escape with the steam.
Despite the name, pilsner malt is not limited to lager. Brewers also use it to make a wide range of ales.
Increase the kilning temperature and the malt begins to take on a deeper colour and more pronounced aromas. Vienna and Munich malts can bring bread crust, toast, biscuits and nuts, often contributing an amber colour to the finished beer.
These highly kilned malts have less enzyme activity than paler base malts, so they are commonly used alongside them. Some still retain enough enzymes to make up a substantial part of the recipe.
At higher temperatures, roasting produces dark malts with flavours of coffee and chocolate. These malts can also contribute bitterness and some acidity, along with the brown or black colour associated with porters and stouts.
Chocolate malt, brown malt and black malt are examples. Roasted unmalted barley can create similar characteristics and is commonly used in Irish stout.
Caramel and crystal malts follow a different route. Green malt is heated while it is still moist, allowing enzymes to convert starch into sugar inside the grain. Further heating then develops colour and flavours such as caramel, dried fruit and candy floss.
These malts can also give beer a reddish hue and contribute sweetness and body.
Smoking offers another possibility. Malt exposed to woodsmoke can carry aromas of woodsmoke, smoked bacon or smoked cheese into the finished beer. Beechwood-smoked malt is closely associated with Rauchbier, the smoked beer style for which Bamberg in Bavaria is particularly well known.
Choosing malts for a beer
The combination of malts and grains used in a beer is known as the grain bill.
Base malt usually makes up the largest share because it supplies the starch and enzymes needed during mashing. The brewer can then add smaller amounts of other malts to change the colour, aroma, flavour and texture.
A pale lager might rely heavily on pilsner malt for its light colour and delicate cereal character. An amber beer could include Vienna or Munich malt for toast and biscuit notes. A stout may combine pale base malt with chocolate malt, black malt or roasted barley to build its dark colour and roasted flavours.
The proportions matter. A small amount of dark roasted malt can change the appearance and aroma of an entire batch. Too much may introduce harsh bitterness or overwhelm the other ingredients.
Barley is not the only grain available. Wheat, rye, oats and other cereals can also be malted and used alongside barley.
Malted wheat can contribute a smooth texture, support foam and create the hazy appearance found in many wheat beers. In Weissbier, for example, malted wheat normally makes up at least half of the grain bill.
Rye can bring its own distinctive flavour and texture, while oats are often used to give beer a fuller body and silkier impression.
Some recipes use a single malt. Others combine several malted and unmalted grains. Each choice changes what the brewer has to work with before hops and yeast enter the picture.
When brewers use other fermentable ingredients
Malt is usually beer’s main source of fermentable sugar, but it does not always work alone.
Brewers may add unmalted grains, sugars or syrups to create a particular style, adjust the beer’s body and flavour or change how much of the available sugar the yeast can ferment. These ingredients are often known as adjuncts.
Unmalted barley, wheat, oats, rice, rye, maize and sorghum can all be used in brewing. As they have not been malted, they do not provide enough active enzymes to convert all their starch into fermentable sugar. They are therefore usually used alongside malted barley.
Different grains have different effects. Rice and maize often produce a lighter flavour and body and are closely associated with many American lagers. Wheat can contribute smoothness, haze and foam, while oats can give beer a fuller body and silky texture.
Sugars and syrups behave differently. Many are highly fermentable, so yeast can convert them into alcohol efficiently. Adding them before fermentation does not necessarily make the finished beer sweet. They can increase the alcohol level while keeping the body relatively light.
Some contribute little aroma. Others have a distinct character of their own.
Candi sugar, used in some abbey-style ales, ranges from pale and relatively neutral to dark and rich, with flavours of caramel, raisins or dates. Honey, maple syrup and black treacle can also provide fermentable sugars and add their own aromas to the beer.
When a brewer wants sweetness to remain after fermentation, an unfermentable sugar may be used. Most standard brewing yeasts cannot ferment lactose, for example, so it stays in the beer and can create a sweeter, fuller impression.
Identifying malt in the glass
Malt has already shaped much of a beer before fermentation begins.
It may appear as bread and honey in a pale lager, toasted nuts in an amber ale or coffee and dark chocolate in a stout. Wheat can support foam and haze, oats can soften the texture and smoked malt can leave a character reminiscent of a wood fire.
The next time one of those flavours appears in a beer, look to the grain bill. It began with choices made during germination, kilning and roasting, followed by the brewer’s decision about which malts to bring together.
