An Introduction to Malted Barley

What is malt and why is it so special?  No malt, no beer.  Thank you for reading. 

In the universe of beer and brewing, malt usually refers to malted barley. While beer is made from many a grain, and many a grain is malted, barley is the most prevalent in Western beer brewing for several reasons. First off it contains all the indigenous enzymes required to convert its own starch reserves into fermentable sugars. In other words, it’s the whole package. Yes, wheat and rye also have the enzymatic power to self convert but they can cause a sticky mess if used in isolation. Barley has a thick husk, whereas wheat and rye have little to none. The barley husk is also very hard to break down which is important for improving drainage in the mash. The mash is the step in the brewing process where the grains are steeped in hot water to extract the sugars which are then fermented into beer. Barley husks are like the aggregates in garden soil, allowing the wort ( beer) to flow through. Barley is also much lower in gluten than wheat or rye. Rye has a third of the gluten of wheat, but even at that level, issues can arise. Glutens are a group of proteins that can link together to make a stretchy, sticky kind of dough. The takeaway here is that a mash of 100% wheat or rye will be a big sticky undrainable mess, and so best to avoid without some accomodation. A lot of beers are brewed with wheat and rye and oats, but invariably alongside a decent amount of barley, and often including rice hulls for drainage. This is a topic for another day. 

From the humble seeds of a hardy grass, through the careful work of the diligent maltster, opens a world of flavour. Bread, cracker, biscuit, caramel, toast, bread crusts, raw dough, nutty, toffee, dark fruits, molasses, burnt sugar, treacle, honey, chocolate, coffee, roast, and burnt grain are amongst the vast array of flavours that can be extracted from malt. 

The Barley

Let’s start in the field. Barley (Hordeum Vulgare Spontaneum) is a cereal grass that is closely related to wheat and rye. There are two main barley varieties of concern, two-row and six-row. A four-row variety exists, but no one seems to bother much with it. The names come from the number of rows of kernels running up the tip of the stalk, an area called the rachis. (see illustration). If you were to look from above, the number of rows are like the spikes on a star, even if one variety is a two-spiked star. Two-row is abundant in Europe, while six-row is more common in the USA as it is a little more tolerant of the warmer climate. Six-row is in fact two-row, with a mutation in the VRS1 gene. There are several main differences between these two barleys. Six-row is higher in protein, this is good for providing amino acids to the yeast but can become a bit of a clarity issue down the road. Six-Row is lower in saccharides, which of course means fewer fermentable fractions. Six-row has a thicker husk, excellent for drainage, but poses issues with the excess extraction of polyphenols. Six-row contains higher amounts of enzymes. This is great for adjunct brewing where the excess enzymes can get to work on any grist additions that can’t self convert, like corn or rice.  Lastly, six-row has higher levels of S-methylmethionine, the precursor for Dimethyl Sulphide, which is the canned corn or cooked cabbage smell in some beers. While often unavoidable at low levels, this tends to be something we don’t want very much of.

2-Row 6-Row

According to the USDA, 143.6  million metric tonnes of barley was produced globally for the 2024-2025 marketing year. Of this, 35% was grown in the European Union, followed by 11% from Russia, 9% from Australia, and with Canada and the UK coming in with 6% and 5% respectively.  

About 70% of cultivated barley is destined for animal feed, in which case a higher protein variety is desired. The remainder is grown for malting, to make beer and other alcoholic beverages, such as malt whiskey, with a small portion reserved for human food. There are two main types within the types, winter barley, which is sown in fall, and spring barley, which is sown in spring. It takes around 60-70 days for barley to grow fully and a total of 120-130 days to reach full maturity.  Most of the barley destined for malting is spring barley. 

A fairly hardy and resilient plant, barley can tolerate a wide variety of climates as well as soil conditions. Barley is fairly drought tolerant, and can also tolerate soil with higher alkalinity than other cereal grasses, contributing to its abundance. It does however, prefer well drained soil, lower temperatures of around 15-20°C, and dryer conditions.

It’s not all fun and games in the barley field however. Like any agricultural endeavour, disease and pests lurk in every dark corner. Aphids, powdery mildew, rust (a fungal infection), and other common field pests all pose potential threats. Two of the biggest problems though are fusarium head blight (FHB), also called scab, and Ergot. FHB is a fungus which causes shriveled kernels that can appear white. More seriously, FHB creates a mycotoxin, (a toxin produced by a fungus) called Deoxynivalenol. Deoxynivalenol, is a trichothecene, which are highly toxic sesquiterpenoids. The toxin often goes by the romantic name “ Vomitoxin”, I’m sure you can guess why, or simply, DON. A less serious, but potentially messy effect of DON is gushing. Gushing is when you open a beer, and it foams out of the bottle all over the place, without being provoked by agitation. The second major potential infectant, which sounds like a member of the weasel family, is Ergot. Ergot is another fungal infection which produces a group of alkaloids that if ingested, can cause, among other things, seizures and burning limbs. These conditions have been referred to as “St. Anthony’s Fire”. Another weapon in Ergot’s arsenal is its ability to produce Lysergic Acid, the precursor for Lysergic Acid Diethylamide, which you might simply call LSD, or maybe Lucy, or maybe just Acid, depending on your leanings. Burning limbs, seizures, and  hallucinations!. It goes without saying that none of these are particularly desirable, and agricultural methods of control are widely employed. Analysis is done on malting barley to ensure none of these toxins are going to make their way into your beer. As fun as they may sound. 

Into the Malthouse

Now that the barley has been grown and harvested and presumably cleared of any hallucinogenic toxins, it is shipped to the malthouse. The malting process, in a nutshell, or in a barley kernel perhaps, is as follows. The grain is allowed to partially germinate, germination is then arrested, and the grain is heated until desired colour and flavour products are achieved.

Barley arrives at the malthouse at around 12% moisture of total weight. It is then steeped in water for 1-2 days until the moisture is up to 40-48% of total weight, causing it to almost double in size. Either air is forced up through the bottom of the bed, or air rests are employed to ensure an adequate supply of oxygen. Unlike in photosynthesis where CO₂ is respired, O₂ is required for germination. Aerobic respiration is key to glucose breakdown. When target moisture is reached, the barley is left to germinate. Historically, a technique called floor malting was employed. This is exactly how it sounds. The malt is spread out on a floor, and systematically plowed or raked. Some traditionalists and smaller operations will still use this method. Major producers however, employ more modern techniques known as pneumatic malting, whereby forced air circulates through the grain. Two major designs for pneumatic malting are the drum malter, which rotates, and container malting, or saladin box. For the latter, a large rectangular vessel with a perforated bottom holds the grain while large vertical augers turn it. Other systems like continuous malting, and tower malting exist and are used. 

As the barley germinates, rootlets start to emerge. These are called chits and will become tangled with one another if allowed to, and cause a general ruckus. The manual or mechanical churning of the malt prevents such tangling.  

What happens during germination is of vital importance. The embryo begins to develop, the acrospire, which eventually would turn into the stalk of the new plant, begins to grow, and enzymes begin to break down the protein matrix in which are locked the starch reserves. The degree to which these are unlocked is called modification. The germination process takes 4-6 days. Once the malt is sufficiently modified, and it is crucial that modification is adequate without going so far as to allow the embryo to start eating up those starches, a process called withering begins. Withering uses fans to dry out the malt somewhat, also causing the rootlets to wither. We now have what is called green malt.  

Barley, and consequently malted barley, consists of 60-70% carbohydrates, mainly in the form of amylose and amylopectin, along with some amounts of dextrins, sucrose and fructose. During malting, some of the amylose and amylopectin are broken down into glucose, maltose, maltotriose, and maltodextrins. Around a 6-8% reduction. The remainder stay in longer chain form to be broken down further in the mash.  

The main proteins, which constitute 10.5-15% of dry weight, are in the forms of hordein and glutelin, both which are storage proteins. During malting, a group of proteolytic enzymes break apart these proteins into smaller peptides and amino acids. Hordeins are broken apart more easily than glutelins. The degree of protein modification is measured by the ratio of Total Soluble Nitrogen to Total Nitrogen, reported as the Kolbach Index. Soluble proteins are essential for yeast health but too much protein can have negative impacts on the finished product.

Around 4% of barley is made up of lipids and fatty acids, around 70% of which are triglycerides, and are mostly found in the aleurone layer. A bit less than 20% are fatty acids, mostly linoleic acid, palmitic acid, oleic acid, and linolenic acid. The remainder are sterols and steryl glycosides. These lipids and fatty acids get reduced to around 1.5-2.5% as they are hydrolyzed and used up as a source of energy during germination.   

The cell walls of barley are mostly constructed from beta-glucans, hemicellulose, and cellulose.  The beta-glucans are the biggest fraction and are significantly broken apart by glucanase enzymes into smaller chains (maltose, and dextrins) which will eventually be broken down into individual glucose components. The hemicellulase enzymes partially break down the hemicellulose, but leave a significant portion intact. Cellulose is not readily degraded by enzymes and remains mostly intact. Polyphenols, which also reside in the husk and cell walls are also not readily degraded by enzymes. A type of polyphenol called tannins contributes to the astringency of the beer. Polyphenols also contribute to chill haze. 

Small amounts of minerals and vitamins including some B vitamins, iron, potassium, calcium, magnesium, phosphorus are also present in the barley kernel. These are key to yeast health.

So at the end of this process, just before we jump in the kiln, we’ve reduced some of the longer chain starches into sugars, broken down a significant chunk of the protein matrix, unlocking the starches, broken down and metabolised some of the triglycerides, and released an army of enzymes. The two major enzymes of concern are alpha-amylase and beta-amylase. Other enzymes present are proteases, proteinases, beta-glucanases, cellulases, collagenases, pectinases, hemicellulases, pentosanases, phytases, peptidases, glucosidases, dextrinases, and phosphatases.  

Into the Fire

The primary objective of the kiln is to halt the germination process. Since the goal isn’t to grow plants, and a certain level of starches are essential for fermentation, the moisture level needs to be reduced significantly. Lest we get no beer. The secondary objective is to heat the malt until target colour and flavor qualities are reached. This is done in the kiln, or in the case of the darker roasted malts, in a drum roaster. Enzymes can be rather fragile and rapidly denature above a certain temperature. Denaturing means they unravel, and once unravelled, they do not re-ravel. The damage is permanent. The key to remember is, the darker the malt, the lower the enzymatic potential, which is why the darker malts are used as colour and flavour additions, and not as the primary fermentables. The dried up rootlets are now knocked off, the malt is cleaned and screened and moved to a storage bin for the moisture to further equalize. 

Base malts are categorized as malts with enough enzymatic potential to not only self convert, but to convert everything else that goes into the mash. This means roasted malts, colour malts, and adjuncts such as corn, rice, unmalted wheat.  

The Flavours and Colours

So what happens in the kiln or roaster? Two transformations occur. Caramelization and the Maillard Reaction. 

Caramelization is the breakdown of sugars via thermal decomposition, or pyrolysis. In other words, bonds are broken. A simple example is the breakdown of sucrose, which is composed of one glucose and one fructose molecule, to the individual sugars. The temperature at which this occurs varies by what sugar is being broken down. The degradation temperature for glucose for example is 150°C. Unfortunately the process is still not fully understood, but what does happen is the colour changes and the flavour changes. The brown colour is created by three groups of polymers, Caramelan, Caramelen, and Caramelin. I know that sounds made up, but it’s not. Also during the process a number of aromatic compounds are produced and released. A few lactones and esters, some furans, maltol, and one all us beer fans are familiar with, diacetyl. Diacetyl is that popcorn butter aroma present in some Czech Premium Lagers, as well as movie theatre popcorn. Most of the diacetyl in beer however is a fermentation byproduct. Caramelization accelerates in both acidic and alkaline conditions, and is slowest at a neutral PH.

The second colour/flavour process is the Maillard reaction. It is similar to caramelization but occurs when amino acids along with reducing sugars are heated to around 140-160°C.  Specifically, when the amine group of an amino acid reacts with the carbonyl group of a reducing sugar in the presence of heat. A reducing sugar means a sugar that can act as a reducing agent, meaning it can act as an electron donor in a reaction. A carbonyl group is a carbon atom double bonded to an oxygen atom. There isn’t really a simple way to explain that but we’ll get in depth on reduction reactions another time. It’s also a multistep process, which in itself might be a bit too far down the rabbit hole. Even for me. 

The results of this reaction are melanoidins and a group of heterocyclic compounds. Melanoidins are a high-weight heterogeneous polymer. Their chemical structure is again not fully understood. Melanoidins are brown though. We know that much. The second product is a group of heterocyclic compounds, which means it’s a ring structure where at least one of the atoms is not carbon. These include furans, pyrazines, pyrroles, thiazoles, and thiophenes. These are the contributors to the aroma and flavour. A few other glucose degradation products and various dicarbonyls are produced as well. A few quick points on Maillard before we move on. The degree of browning depends on both the amino acids involved, and the sugars.  Disaccharides react the least, hexoses ( six molecule sugars) slightly better, and pentoses (five molecule sugars) the best. This means sucrose, lactose and maltose will react the least, glucose and fructose slightly better and ribose the best. These are just examples from each category. The Maillard reaction produces water as a byproduct, so a high water condition will slow or even completely inhibit the reaction. The browning crust on grilled chicken is an example of a Maillard reaction. Boiled chicken is a different story. 

The Malts

Base malts are a classification of malts that contain enough enzymatic power to not only self convert, but to convert any enzymatically inactive adjuncts added to the grain bill. When we mash, we steep the crushed malt in hot water to release the fermentable sugars for the yeast to digest and transform into beer. The malt itself contains a mix of polysaccharides, or starches which are at this stage indigestible by yeast. The barley’s indigenous enzymes start breaking those starches apart into fermentable shorter chain sugars. We will discuss this further in the future. Recall that enzymes are destroyed above certain temperatures, so the malts kilned at the lower temperatures are going to be the ones with more enzymatic potential.

Malt colour is reported in °L (Lovibond), EBC (European Brewing Convention) or the ASBCs SRM (Standard Reference Method).  We shall use °L.  Not for any real reason other than it seems to be more common. 

Base Malts

Pilsner Malt  1.4-2.22 °L

Produced in the United Kingdom and continental Europe from two-row barley, this is the basis of most European pale beers.  It is kilned at around 80-85°C, and is low modification. Higher levels of S-Methylmethionine, the precursor to dimethyl sulphide, is present in the malt.  DMS is the cooked cabbage, canned corn smell present at low levels in some lagers.  

Lager Malt 1.4-2.2 °L

Also called pale malt, predominantly produced in the USA from 6-row barley.  Very good for adjunct brewing as it has high enzymatic power.  The malt also has high FAN ( free amino nitrogen) suiting it well for the adjuncts’ contribution to lowering overall protein.  Typically kilned 80-85°C. 

Pale Ale Malt 2-4 °L

Mostly produced in the United Kingdom and Belgium, pale ale malt gives that slightly malty edge to English style ales.  Fairly well modified and lower in SMM than some other base malts.  

Vienna Malt 3-4 °L

Vienna gives that lovely amber orange colour to the beer along with a nutty, toast and caramel flavour.  Kilned at 90-95°C, it retains good enzymatic power.

Munich Malt 6-12.5 °L

Munich has a fairly wide colour range, and imparts toast and caramel to the beer.  Enzymatic power is on the lower end, with enough to self convert, but not enough to share.  It can also be used as a flavour addition to drop malty notes into a beer.  Kilned at 100-105°C.

Melanoidin Malt/Honey Malt/Brumalt 15-33 °L

A sort of jacked-up munich malt, and viewed as a way around decoction mashing, this one has a sweet honey like flavour and is well modified. Usually can self convert but would be a flavour bomb so is used sparingly. It is kilned at 100°C and has higher moisture going into the kiln.  

Caramel Malts

Caramel malts are a style of malt whereby green malt is loaded into a drum roaster, without being dried out.  Typically the malt is germinated at a higher temperature and initial kilning/roasting happens in the presence of steam until this liquifies the sugars and then allows them to recrystallize giving the malt a glassy texture. Essentially it is mashing in the husk. This makes these malts less fermentable, and so they are used to add body to the beer.  The higher protein helps with head retention.

Special glassy 

Also called dextrin malts, or Carapils, they add body and sweetness and boost head retention. 

Caramel/Crystal Malt 10-140 °L

Coming in a variety of colours, they contribute to both flavour and colour and one has to be rather careful with them.  Pale tends to be 10-30 °L and is kilned at 155-180°C, medium 40-80°L and kilned at 180-210°C and Dark 100-140°L, kilned at 204°C

Roasted malts

Pale malts are loaded into a drum roasted and roasted. They are drier, more astringent and dark. Mostly used for colour addition or some roasted burnt flavour, they almost never exceed 10% of the grain bill. The high temperature destroys all of the enzymes, so they cannot self convert.

Biscuit 15-23 °L

Roasted up to 227°C it adds a bread crust, toast like flavour, and is a key feature in brown ales.  

Amber Malt 20-30 °L

This is a slightly more complex process.  First, a low moisture malt of around 4-5%, is heated to 93°C quite quickly and then the temperature is slowly raised to 149°C. The flavours of toffee, bread and nuts develop and the dry roasting process develops some pyrazine and pyrrole which contribute some bitterness to the finished product.

Brown Malt 50-65 °L

Roasted at 177°C a bit of extra time gives it more colour and flavour than amber.  Flavors include toffee and bread. It adds some nice brown colour to the beer, but too much can make the end product harsh.

Chocolate Malt 200-400 °L

Roasted at 216-232°C but is halted before it turns black. Slightly astringent and mildly burnt, the maillard reaction produces coffee and chocolate like flavours. 

Black Malt 475-600 °L

Roasted at 216-232°C this malt gives a huge colour addition and a little goes a long way. A non-negotiable for stouts, the malt imparts a dry burnt bitterness.  A debittered, huskless variation can add colour without astringency.  

Roasted Barley 500

Not malted, just roasted. It is milder than roasted malt and key in dry Irish stouts. Roasted barley contributes to a lighter coloured foam than the equivalent malted version in a beer of the same colour. 

Specialty Malts

Acidulated Malt 2.2-4 °L

Also called Sauermalz, it is effective in lower mash PH while remaining on the right side of the Renheitsgebot. It is acidified by allowing Lactic Acid Bacteria to grow on the malt.  

Smoked Malts 2.5-5 °L

Smoked malts dried directing over wood, allowing the smoke to penetrate the malt.  Rauchbiers use a heavy grist of smoked malt.

Peated Malt 1.7-2.5 °L

The same as smoked malt but the combustion medium is peat. This is mostly used for scotch whiskey.