Carl began his brewing career in 1987 as a lab technician at Websters Brewery in Halifax, after a short spell at Tetleys Brewery, he went back to Websters as a bottling line manager in 1990.Read More
I was already well-versed in the principles of brewing when I did my first mash back in February 1993. My training in beer flavour and quality in the labs of Webster’s and Tetley’s was second to none; I’d run various packaging lines; and I was a long way through my studying for brewing qualifications. Yup, I had the theory nailed. But I’d never experienced what it was to brew.
My first job as the Process Brewer at Belhaven Brewery was under the watchful eye of much-loved head brewer George Howell. It was wonderful to actually mash a brew, a happy memory to this day. Watching the beautiful, copper-domed mash tun filling with grist. Breathing in the sweet, rich, Horlicks-type smell. Testing the porridge-like consistency. Tasting the wort. Experiencing a malt sauna when at the end, I jumped into the tun to sweep it out.
Science originally attracted me to the world of brewing. The alchemy involved in mashing alone is extraordinary – and we’ll look at it in depth in this post. The better your knowledge about science and process, the more likely you are to produce consistent, successful mashes. But you need more than knowledge to be a successful brewer. As I’ve discovered over the thousands of mashes in hundreds of breweries since that first one, judgement is essential. Judgement is a huge part of the craft. And judgment comes with experience – with endless hands-on involvement. The more you mash, the better your judgement, the better and more consistent your brews. This post is more about the science and the process of mashing – clearly you need to get your hands dirty to develop your judgement.
Mashing is essentially a continuation of the malting process. Enzymes are reactivated by soaking crushed malt (grist) in water at a specific temperature to form a porridge-like substance. The enzymes are then given time to digest the starch, nitrogen and, in some cases, cell wall materials – to make them soluble.
In this post I’ll provide an overview of the important factors to take into account when mashing – and delve a bit into the alchemy behind the process. We’ll finish by talking about the important components of the resulting sugary liquid – wort in its full wonders.
If you’d prefer a more visual approach to this subject then please consider watching our mashing webinar.
Ok, you know this, but even so, let’s just spell it out…
Without mashing there would be very few nutrients for the yeast to metabolise and, believe me, the resulting beer would not be palatable! There are three basic types of mashing process:
Different mashing processes are used in different parts of the world. It all depends on local tradition, the quality of malt available, the brewer’s equipment, and the beer styles being brewed. Most of this blog is about infusion mashing using well-modified UK malt.
In Britain, most of the malt is well modified and low nitrogen. Maltsters here tend to make sure that a lot of the solubilisation of nitrogen compounds and cell wall material happens at the maltings – rather than leaving that part of the work for brewers. That explains why the predominant mashing method in the UK is single-temperature infusion. It’s all because of us maltsters!
Barley in other countries tends to be higher in nitrogen and beta-glucans – which form cell walls in the endosperm of the grain. Maltsters can’t do as much with these raw materials. They can only achieve a limited amount of modification. So it’s down to brewers to mash at stepped temperatures, gradually coaxing the enzymes to digest the cell walls. Also, for you brewers pushing the boundaries with other cereals, these too need to be step mashed.
The table below shows the temperature optima for the enzymes to do their crucial work:
|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|
You need a mash-conversion vessel to deal with this high-nitrogen malt. They don’t normally have the capability to separate the wort from the mash. Their heating jackets help achieve the necessary temperature rises, and they have low shear agitators to homogenise the mash and prevent temperature gradients. The temperature profile is governed by the malt being used and the beer style being brewed.
Once conversion is complete, the mash is pumped to another vessel to separate the wort from the mash. The most common of these is the lauter tun. This has a larger diameter than a mash tun for any given mash quantity, so the bed depth is shallower. The principles of separation are the same as for the mash tun. It has rakes which can gently cut the bed to aid runoff and speed up the separation process.
Another older, and less common method, is decoction mashing. A portion of the mash is removed from the main vessel, raised to the saccharification temperature, converted and then boiled and added back to create a temperature rise. It’s still used in breweries in the south of Germany and the Czech Republic – more for the tradition and authenticity than for efficiency.
The classic version of the double decoction is a shortened triple decoction. It omits the acid rest and starts with the protein rest. Because of this, only two decoctions are needed to get to mash-out. One is to get from the protein rest to the saccharification rest; the other to get from the saccharification rest to mash-out. With well-modified lager malts, this may result in overly extensive protein degradation.
This is the chemistry bit. It’s a little deep so hang in there even if you don’t have a scientific training. You’ll get to love it over time.
The presence of calcium ions in the mash will cause a drop in pH because of their interaction with the abundant amounts of phosphate ions in the malt:
Without calcium ions, the wort pH would be 5.8 – 6.0 pH. That’s too high for the mash enzymes to work effectively. Calcium also has the following beneficial effects:
The released hydrogen ions further reduce the pH – which encourages further precipitation of proteins. Proteins are also degraded, and converted to simpler substances by proteolytic enzymes called proteases. These are found in the malt and have optimum activity at pH values of about 4·5 – 5·0.
The reduction in pH then caused by the presence of calcium encourages proteolysis, getting the protein levels down further (good!) and increasing the wort’s Free Amino Nitrogen – FAN-levels (also good!).
The reaction: Reducing Sugar + Heat Melanoidins are also inhibited.
With all the above advantages of the presence of calcium and reduction in pH there is one disadvantage. The reduction in pH causes a decrease in hop utilisation. That means producing less bitter beers or increased hopping costs to achieve the desired level of bitterness.
One of the main aims of mashing is to degrade malt starches into simpler, fermentable sugars. There are two forms:
These molecules are digested by amylolytic enzymes – α-amylase and ß-amylase
The Limit Dextrinase (LD) is reported to be in resting barley, but mostly LD enzyme is synthesized during germination in the malting process. An LD inhibitor is also expressed during germination – and may reduce LD activity during mashing. LD cleaves the α-1,6 branches on amylopectin, producing chains for α-amylase to further hydrolyze into shorter chains. The degree of branching on amylopectin and amylose in barley (or any other cereal used either as malt or as an adjunct source) could impact on the residual dextrins, which are unfermentable. These are solubilised in brewing and remain in beer, contributing to mouthfeel. The temperature of the initial brewing process (as below) influences LD activity, and with the highly branched amylopectin, there could be uncontrolled residual dextrins impacting on beer flavour. LD is thought to be quite temperature sensitive, but data suggests that it can withstand a reasonable time in a mash and by releasing chains makes a significant contribution to fermentable sugars.
Let’s take a look at some of these facts in graphical form:
At 63°C mash temperature:
At 65°C mash temperature:
At 68°C mash temperature
Sparging with liquor below 78°C or sparging for too long will increase fermentability as the α-amylase will not be inactivated.
Choosing the right ratio of liquor (litres) to grist (kilogrammes) will affect the alcohol content and mouthfeel of the final beer. Create appropriate mash thickness and get the right temperature for the style of beer to be brewed
The variables described above affect the types and quantities of sugars created during the mash stand. Yeasts vary in their ability to metabolise the different types of sugar produce by the mash. Work out which yeast strains to use to ensure that the beer hits the mark.
Here is a typical wort sugar spectrum:
The nitrogen in wort comes from the malt. The higher the total nitrogen content of the barley used to make the malt, the higher the levels of soluble nitrogen nutrients and enzymes in the wort.
During germination at the maltings, the grains synthesise proteolytic enzymes to break down the storage proteins in the endosperm.
Endoprotease enzymes produce peptides and polypeptides. 90% survive kilning, but they decompose quickly during mashing at 65°C. Their activity can be utilised in a stepped-temperature mash, with optimal activity at 50 – 54°C.
Carboxypeptidase enzymes produce amino acids. They survive kilning and some can be moderately active up to 70°C in the mash – which can be important if there is a deficiency of soluble nitrogen in the malt.
At the end of the mash stand, the wort will be 3 to 6% nitrogen compounds comprising the following:
Both of these compounds can cause problems in the brewery.
80% of the polyphenols in wort come from the husks of malted barley. They are astringent compounds that can work with haze sensitive polypeptides to create a colloidal haze in filtered and cask beers after a few weeks in package.
Crisp has a proprietary malt called Clear Choice. The barley has none of the polyphenol precursors in the husk. Sweet worts made with Clear Choice are polyphenol-free so produce more stable beers with a smooth flavour.
Beta-glucans and other compounds that make up the cell walls in the grain can cause high-viscosity, sticky worts that are difficult to run off. It’s the job of the maltster to digest as many of these as possible but some barleys are higher in cell wall material than others and the growing environment affects the levels too. Our maltsters vigilantly monitor, and respond to, variations in the raw materials to reduce the beta-glucans and other unwanted compounds.
If high beta-glucan malts have to be used then longer run-off times should be expected unless the brewery can start the mash at 40 to 42℃ and stand for 20 minutes to allow beta-glucanases to break down the polysaccharides into less viscous compounds. Heat stable fungal beta-amylases are also available to add to the mash if necessary.
Of course you know the basic principles. But with any luck, you’ll find something here that adds another string to your bow. Let’s start with ingredients.
The most common cereal used in brewing is malted barley and of course you know why. It’s mainly due to the low gelatinisation temperature, abundant starch and enzyme content.
The malt grains need to be milled, crushed or cracked open through a roller or hammer mill prior to mashing. Any malted wheat, oats or rye you’re using need to be milled on different gap settings to barley malt as the corns are a different size. The particles in the grist are reduced to a size where the enzymes in the malt can begin to digest the starch and nitrogenous compounds.
You can buy all your malt – or just some specific malts – ready-crushed. Some brewers who buy whole barley malt, also buy ready-milled oats, wheat, or rye to save adjusting the mill – which can be a tortuous process and which often leads to errors.
Unmalted cereals such as oats, barley, maize and rice can also be added prior to mashing in flaked form if they’ve been pre-gelatinised by micronisation or torrefication.
Check out grist in our milling blog.
The ionic content of water varies depending upon where it’s drawn from – private borehole, spring or mains. Water with high alkalinity (resistance to change in acidification by H+ ions) needs to be treated to achieve the correct mash pH for optimum enzyme activity. I like Murphy and Son’s explanations of water chemistry and treatment. Take a look and see what you think:
Certain styles of beer require a specific ionic content and this can be achieved by adding food grade salts such as Calcium Chloride, Calcium Sulphate, Magnesium Sulphate and Sodium Chloride. I’ll touch on this again in mash chemistry.
So, let’s assume that we now have the right blend of crushed grains and water that’s suitable for the beer style being brewed. Time to mix them together and mash in.
Temperature is fundamentally important when creating a mash. There are four things that affect the final mash temperature:
The water temperature in the hot liquor tank will not necessarily be the temperature at the point where the liquor and the grist meet. Any losses on the way to the point of mixing should be compensated for in the hot liquor tank temperature set point.
Might be obvious, but it’s worth saying: if the crushed grains have been sitting in a cold place, they will bring down the temperature more than if they’ve been stored somewhere warm. You need to take this into account – and might need to follow the example of other breweries, which use different hot liquor tank setpoints in summer and winter. Check out our malt storage guide for best practice on storing malt.
The ratio of the liquor (litres) to grist (kilogrammes) will also affect the final mash temperature.
Cold brewing vessels and pipework reduce the temperature of mashes. A good practice is to preheat the mash tun by adding hot liquor to the vessel through the sparge arm. However, care should be taken not to use up too much water: you need to leave yourself enough for mashing and sparging.
Before mashing begins, take a note of the amount of hot liquor in the hot liquor tank – if your HLT doesn’t tell you how much is in there, install a dip tube and calibrate it using:
volume =𝜋r2h (Remembering to account for any dished or conical bases on the vessel).
An alternative is to install an in-line flowmeter by the hydration point. These guys make good ones and they’re pretty cheap:
Knowing the amount of hot liquor is important since you should have a fixed liquor to grist ratio for each beer brewed, depending on the beer style.
Discard any liquor in the mash tun that was used for pre-heating, close the outlet valve and then add sufficient hot water to cover the plates. This is called foundation liquor and it protects the grist particles, preventing fines going beneath the plates. Ensure that this is factored into the mashing in liquor calculations.
With the liquor flowing at a steady rate, introduce the flow of grist, again at a steady rate. In an ideal world, there should be some sort of device that pre-mixes the two before they hit the mash tun. These are called hydrators and you may be lucky enough to have a Steels Masher – a mechanical device invented to ensure a good mix of liquid and solid. Whether there is a hydrator or not, the mash mustn’t have any un-hydrated lumps.
If you’re mashing in manually, follow the same principles of even flow as the liquor is filling the tun, and gently mix with a paddle. Take care not to overwork the mash – as this will cause problems. Aim for the flow of grist to stop slightly before the flow of liquor so that the hydrator is flushed out.
Mashing should be done in no longer than 20 minutes. Once complete, make a note of the time, then measure and record the actual mash temperature and pH.
Once the mash is completed, the lids should be replaced on the mash tun to keep the mash warm.
The mash will now need to stand for between 45 and 90 minutes depending on the beer style and grist composition. The aim is to convert all the starch into more simple sugar molecules and this can be checked by using an iodine solution at the end of the stand period. Here’s a diagram of what happens to the starch and how it reacts to iodine:
Once the stand is complete, the outlet valve of the mash tun should be opened up to about half way. The initial wort, that’s the sweet nutrient rich solution that’s just been created, may be cloudy and have small particles of malt in it. The best thing to do with this is gently put it back on top of the mash, ensuring that it’s as evenly spread across the bed as possible. Doing this will allow the husks in the mash to clarify the wort. The German brewers call this vorlauf. It can be done through the wort run-off pump or with a bucket or jug.
Once the recirculation of cloudy worts is done, the wort can be directed to the wort kettle for a few minutes and then it’s time to start sparging. Sparging is the process by which hot liquor between 75 and 78℃ is passed through the mash to wash out the residual sugars and other nutrients. It’s important the temperature is maintained between this range to inactivate the α-amylase enzyme in the mash, otherwise the wort will be too fermentable. You may need to increase the temperature of the HLT during the mash stand. You can also ensure that you have enough hot liquor left to achieve the correct sparge volume.
The sparge liquor flow rate should be the same as the run-off flow rate to keep the mash bed afloat. Spend some time getting this balance right before going off to do other jobs like getting your hops weighed out. The top of the bed should either be just covered with sparge liquor or be visible just below the bed.
Once the required quantity of sparge liquor has been added to the mash tun, open up the run-off valve fully to keep the bed nice and tight. Keep an eye on the wort clarity towards the end of the run-off and run to drain when the wort goes cloudy.
Most of the talk so far has been about malted barley, but what about other cereals, in their raw, gelatinised or malted state?
One of the most widely grown cereals in the world, it can be used in its raw state, crushed or as a flour; torrefied then crushed or flaked; or of course as a malt. It’s a huskless grain so the quantities in a mash are limited as husks are vital for bed formation and wort filtration.
Wheat is higher in nitrogen and glucans too which, again, can limit the quantities being used. But inclusion of some wheat has a positive effect on head retention and if used torrefied, it doesn’t have a detrimental effect on beer clarity.
Rice is another widely grown, gluten free cereal that is used in many global beer styles. It has a higher gelatinisation temperature than those used in brewing mashes.If purchased raw (usually in the form of broken rice), it has to be cooked in a separate vessel at 75℃ for 45 minutes before being added to the mash. This means it will cause a temperature increase when it goes in.
For breweries without a cereal cooker, the rice can be bought pre-gelatinised in torrefied flaked form. It can be added up to 20% of the grist but must be blended in with the malted barley. Rice gives a clean crisp finish to beers. It can dilute the nitrogen in a mash if the malting barley is higher than desired.
Crushed maize, or grits have to be cooked at 85℃ for 60 minutes to gelatinise the starch before being added to the mash conversion vessel. Similarly to rice, it can be bought pregelatinised in torrefied flaked form and can be added at the same rate as rice when blended through the grist. It imparts a corny, creamy flavour to beers in excess of 10% of the grain bill.
Oats gelatinise at 53 to 57℃ so can be added directly to a mash. They are high in glucan and give up soluble fibres into the beer imparting a smooth mouthfeel. The husk to endosperm ratio in normal oats is high, so at Crisp we malt naked oats that shed their husk at harvest. This means they provide a higher extract for a given weight.
Husked, malted oats can be useful for providing filter material in the tun as oats can cause high viscosity wort due to the glucan content. Oats can also be used in flaked torrefied and rolled form, with the latter providing more extract as they are huskless. They can be used up to 16% of the grist when distributed across the grist. Beyond that they will slow down run-off too much. Oats impart a pleasant sweet cereal flavour, create a smooth mouthfeel and provide a stable haze.
This is what makes the ears of most brewers and distillers prick up. After all, why wouldn’t you want to get the most out of your ingredients?
The amount of sugar extracted from the malt is governed by a range of things;
To calculate extract efficiency in percentage terms;
Litres of wort collected x specific gravity at collection
It might seem obvious, but that doesn’t mean that all brewers remember to do it every time! By noting the following times on the brewing record, turnaround times can be monitored and optimised:
Wort fermentability is fundamentally affected by grist composition and mashing regimes. Measuring the core fermentation time from collection to cooling applied along with the percentage of gravity attenuated will highlight any issues with raw materials or mashing.
Mashing is the first, and arguably most important, step in brewing. Any failings at this stage will have an impact not just on the rest of the process, but also on the final beer itself. It’s a nightmare when that happens, particularly when you know it was avoidable.
Controlling the grist composition and particle size, then hydrating it with the correct amount of liquor at the right temperature will get the process off to a good start.
Attention to detail around time and temperature are critical – as are balancing the flows and keeping the mash bed afloat.
So here’s my advice for what it’s worth. Be as excited about every mash as you were about your first. Meticulously follow the processes and procedures. Turn to the science to inform your decisions. Keep that sense of awe and wonder. Never stop developing your understanding, skills and judgement: they are your craft.
Great mashes make great worts – which in turn create the bases for tasty beers, whatever style, colour, flavour and strength you are brewing
Of course there’s no “one size fits all”. Each brewery is different. We’d love to hear about yours – especially (though not exclusively) if there’s a chance to give you a hand.
Yes, we provide consistently fantastic malts that perform predictably in the brewhouse to give you nutritional worts with great flavour and colour. But we do so much more than that. We advise and support. We share our experience and expertise. We relish any opportunity to help with recipe creation or with solving issues around anything connected with brewing and beer.
Just give the sales team a shout: 01328 829391 or email firstname.lastname@example.org