Malt and Brewing

At this point I’m going to assume you are familiar with the basic principles of brewing. You know what malt, hops and yeast are and have a basic understanding of fermentation. If not then take a look at the earlier categories such as “Brewing with Malt Extract and Hops” where these topics are covered.

In this section we will look into more detailed aspects of brewing, in particular how to process ingredients from their raw state into beer just as a commercial brewery would.

Malting From Barley to Malt

Fermentable sugars are required to make beer, and Barley is the most common choice to provide fermentable sugars and has been used for many hundreds of years. It has a number of attributes that make it ideal for brewing and one of those is the ease of which it can be processed (malted) then utilised by the brewer by mashing to create an ideal habitat for yeast to turn the sugars created during the mashing process into alcohol.

Barley is the seed of a grass. Of all the cereal grains Barley is one of the hardiest and can tolerate a fairly wide range of growing conditions. The kernels grow in rows along the head of the stem in either 2, 4 or 6 rows and you will often see this noted when you come to buy malt. Two row is primarily used in Europe whereas 6 rows of grains clearly yields more barley so is a lot more economical to grow.

The grains are harvested when they reach full ripeness and are stored until the moisture level drops from around 20% to below 14% when they become ready for malting.


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Malting – How It Works

Malting begins by steeping the barley in water, with the barley absorbing up to half of its weight in water. The water is then drained away and the barley is ready to germinate. The barley is spread out in a layer and kept at controlled temperatures to provide the ideal conditions for the barley kernel to begin the process of growing and germinate. The barley is turned with rakes and carefully monitored until it reaches the correct point to halt the process.

Germinating the barley transforms the grain, to begin with the endosperm (the starchy insides of the grain) is broken down by enzymes within the seed. The starches in the endosperm are transformed into simpler carbohydrates and sugars which are used to help the grain grow but are also the exact sugars you need for brewing.

The maltster turns the grain for several days until the endosperm becomes modified, allowing enough time for the starches to break down as much as possible. The barley is now ready for drying and kilning.

Drying & Kilning

A kiln is effectively a large room where the grain is sat usually over multiple levels with the temperature being raised in the room and ventilation in the room being adjusted to first dry the grain at fairly low temperatures and then cure it at a higher temperature

Much of the flavour and the varieties of colours of malted grains comes from the drying and kilning processes. Kilning and then roasting the grains creates reactions called Mailliard reactions. This reaction is what gives food browned during the cooking process its desirable flavour, for example when you caramelise onions they turn brown and become sweet. The exact same reaction occurs when grains are kilned. By controlling the temperature of the kilning process a huge variety of flavours and colours can be produced from the very same raw ingredient.

Before the drying and kilning process starts the grain is known as green malt, the rootlets that formed when the grain was germinated is still attached and these are broken off and removed during the kilning process.

Depending on what type of malt is being produced, the kiln is set to a certain temperature with the grain being dried at this temperature for a determined period. As an example pale malts are dried at a temperature around 40°C with high ventilation for up to 24 hours. Once the moisture content of the green malt falls below 10% the temperature of the kiln is raised to around 95°C for about 5 hours.

Drying the malt slowly at low temperature prevents the enzymes needed for mashing from being destroyed. In the case of a malt like Munich malt which is slightly darker than pale malt the drying phase in the kiln is usually at 50°C and the moisture content is higher at around 20% before being kilned at 105°C for 5 hours. This higher moisture content means some of the enzymes present in the grain are lost, this is why munich malt has less diastatic enzymes, which are needed for mashing than pale malt.

Roasting malt

Once malt is kilned there is also then the option to transform the malt completely by roasting or toasting it. To do this a barrel roaster is commonly used which consists of a rotating drum that is heated from beneath with water sprayers to stop the malt from burning too quickly.

The barrel roaster can take a very light pale malt and turn it completely black with any number of possible shades in between by adjusting the time and temperature the malt is held at in the barrel roaster. This process of toasting or roasting the grain destroys the majority or all of the enzymes required for conversion in the mash, the enzymes to convert these malts must come from other malts in the grain bill.

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mashingThe term mashing isn’t a good description of what’s happening during this particular stage of the brewing process. What is actually happening is crushed malted barley is being steeped in hot water (which the brewer calls “liquor”) at around 64 – 68°C for around an hour to an hour and a half. There may be other steps involved as well as this but in simple terms this is all that is happening.

It is what is happening during the mash that is of particular interest to the brewer. Firstly the crushed malted barley is hydrated which is important because in the case of the mash, natural enzymes in the malt need the water to be able to work. The brewer needs the enzymes working to break down the starches into fermentable sugars, the malt is crushed to break up the kernels and expose as much of these starches as possible.

The temperature is important because it’s at a temperature of around 64 – 68°C that the enzymes we want working start converting the starches to sugars. The brewer can control the temperature for instance aiming at the upper range, 68°C and this will produce a beer with more body as the enzymes leave more dextrins (unfermentable sugars) in the wort. At the lower end of the range the enzymes convert a lot more of the starches to fermentable sugars making a thinner more fermentable beer.

This mashing procedure usually takes an hour for the enzymes to convert the starches in the grain to simpler sugars and can involve taking the temperature up through ranges that activate different enzymes.

After the mash is complete the grains need to be separated from the liquid which is now wort. The separated wort is called the first runnings and the vessel used to mash in is usually designed to easily separate liquids from grains and produce a clear wort. The resulting grains are then sparged with extra water whilst the first runnings are being drawn off, sparging rinses the grain to extract all the remaining sugars that are left clinging to the spent grains.


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What The Hell Are Malt Enzymes

So we know that mashing causes starch in your malted grains to be converted to fermentable sugars. The things that are responsible for these conversions are malt enzymes. In this article I want to introduce the basics.

What Is An Enzyme

In short here is a definition from Wikipedia:

Enzymes ( /ˈɛnzaɪmz/) are proteins that catalyze (i.e., increase the rates of) chemical reactions.[1][2] In enzymatic reactions, the molecules at the beginning of the process are called substrates, and they are converted into different molecules, called the products.

If we apply this to brewing in a round about way, the enzymes that are present in malted grains are what transforms the starches into sugar chains, which are then easily digestable by yeast.

Malt Enzymes and Starches

There are a number of enzymes in malt that become active at certain temperatures of the mash and the ones that are most important to the brewer are the enzymes that turn the starches stored inside the malt into fermentable sugars and dextrins.

Starches are long chains of glucose molecules. If you can imaging a big, thick tree branch with lots of smaller branches attached to it with smaller twigs coming from those, then that is what these starches would look like.

The main thick straight limb of this branch is called Amylose and a limb with lots of smaller branches emanating from it is an Amylopectin. These starch molecules need to be broken down in the mash to create sugars that the yeast can consume, the main enzymes to do this are Alpha Amylase and Beta Amylase

Alpha Amylase – Alpha Amylase will break the long amylopectin branches of the starches and create long sugars and amyloses. Alpha Amylase will become most active between temperatures of 67°C – 73°C and a mash favouring these temperatures creates a less fermentable wort with a fuller body.

Beta Amylase – Beta Amylase will eat the smallest twig ends, of straight branches of Amylose, they can only work from the end of a branch and for every cut they make they free a maltose molecule. They also work away at the amylose starches freed by the alpha amylase. Beta Amylase favours temperatures between 55°C and 66°C and will create a highly fermentable wort with less body and a drier finish.

A mash temperature that is a good combination to get both alpha and beta amylase enzymes working in balance is around 67°C and will make a wort that has a good balance between body and fermentability.

Mash Temperatures

There are other enzymes present in malt like protease and beta glucanase that are activated at lower temperatures, to activate these enzymes a step mash is required to take the temperature up through varying temperature ranges from low to high. Modern malt however is well modified and a single infusion mash targeted to balance or favour either alpha or beta amylase will work for most styles of beer.

If you know your beer is supposed to ferment out fully and finish dry you will want to adjust your mash temperatures slightly to target beta amylase to create sugars that are easier to consume by the yeast. A full bodied beer on the other hand requires you to mash a few degree higher and favour alpha amylase.

Other enzyme rests will break down various starches:


Temp °C Temp °F Enzyme Breaks down
40–45 °C 104.0–113.0 °F β-Glucanase β-Glucan
50–54 °C 122.0–129.2 °F Protease Protein
62–67 °C 143.6–152.6 °F β-Amylase Starch
71–72 °C 159.8–161.6 °F α-Amylase Starch

via wikipedia

(Need info on enzymatic rests here)

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Different Types of Mash

The saying goes “there’s more than one way to skin a cat” and this also applies to mashing your grains. I will run you through the basic mash schedules that home brewers can do and what the benefits of each one are.

Mashing is a process to convert the starches in malted grains into fermentable sugars. Different types of mashing vary in complexity and laboriousness, obviously they aren’t just to create extra effort and hassle, they do have purpose and benefits which we will look at now.

Single/Basic Infusion Mash

The infusion mash is the simplest of the three types of mashing I’m talking about here. The infusion mash is so called because you are basically infusing all the grain in water at a single temperature, usually for around an hour. The only thing you need to make sure of is that you maintain a constant temperature to allow the naturally occurring enzymes in the malt convert starches to sugars.

The obvious benefits of this mash is it’s simplicity and ease. You don’t need to constantly tend to the mash and the process is usually the best option for the vast majority of beers you brew. You won’t be able to brew certain beers though. Those that use high proportions of adjuncts or unmalted grains like wheat. Although these make up very few of the vast varities of beers you can make these types of beers you will need to alter the temperature of the mash multiple times using what is called, step mashing.

Step Mashing or Multistep Mashing

Slightly more laborious, depending on your equipment than a single infusion mash is the step mash. Using this type of mash you raise the temperature to certain targets and rest at those temperatures i.e 50°C, 60°C, 70°C.

The brewer calculates these rest temperatures according to the type of beer and ingredients, each rest promotes the activity of certain enzymes. The protein rest for example favours proteolytic enzymes that break down larger protein molecules in the beer, promotes head retention and prevents chill haze.

The thing about step mashing is you need a heat source through the mash to raise the temperature up to each rest, unless you have a way to directly heat your mash tun then it can be a pain to do a step mash. If you use a cool box mash tun then you would need to use a thick mash and add boiling water to raise the temperature, this can be tricky and cumbersome. Step mashes are easier in pots that can be directly heated, whilst stirring the grains to prevent scorching.

As I mentioned before though in some cases a step mash will be required for example when brewing a wheat beer where there aren’t enough enzymes to convert the malt to make fermentables.

Decoction Mash

A decoction mash is the most laborious and is similar in some respects to a step mash. It involves taking portions of the mash (usually a quarter or third) heating this up to boiling whilst stirring and then adding it back to the main mash. This process of boiling sections of the mash is repeated two or three times until the final mash temperature is reached.

This might seem a peculiar way to go about things, but this mashing process came about because a few hundred years ago metal pots big enough to mash in weren’t available. By heating part of the mash large quantities of beer could be made using the available equipment.

As the decoctions are boiled and added back to the mash the overall temperature rises up in steps that simulate those of a step mash giving you rests that allow enzymes to work.

As you can imagine this is a very labour intensive method of mashing and takes the longest time. However many people say that decoction mashing will add a more complex malt profile to your home brew and it’s qualities can’t be achieved in any other way.

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