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A Norfolk barley field

What Happens At The Maltings?

This month we wanted to tell you how to make malt whisky and then we would go on to discuss the importance of wood in producing this iconic product from Scotland and indeed other places. Trouble is, we ought to spend some time talking about malt first. There are many misconceptions about what malt actually is and how cereals are converted into it. A quick literature survey finds – ‘it opens up the kernel’ – messy; or ‘the starch is converted to sugar’ – not quite; or ‘the process of malting is fascinating’ yes, but how do they do it?

Beer is more complex than wine since nature provides a ready source fermentable sugars in the grape. Thus whisky is more complex than brandy too. In cereals, the sugar that nourishes the young plant is bound up in a polymer of glucose molecules called starch. This starch needs to be broken down by first activating enzymes which will convert the starch into sugars. Of course it is not that simple, the starch is held in granules which are surrounded by structural glucans embedded in a protein matrix. Enzymes are activated to break down the entire floury part of the barleycorn. Starch can then be metabolised to produce energy for the growth process while the protein is broken down and rebuilt as cell material. It is the job of the maltster to germinate the barley to get maximum enzyme formation but with minimal growth of the young plant which would otherwise use up potential sugar for the brewer or distiller.

The barleycorn during malting
The barleycorn during malting. On the right the rootlets have grown too much, overgrowth will reduce yield and impede the passage of cooling air.

Beer is made mainly from barley malt, malt whisky is only made from malted barley. Being low in gluten, barley makes poor bread. The German Beer Purity Law, the Reinheitsgebot dating from 1516 was an early attempt to ensure that valuable wheat was not diverted from baking into brewing. This was the world’s first food processing regulation and is still followed today; it has just had its 500th birthday. Barley grows well in a temperate climate and particularly well in a maritime one thus British barley yields malts which are highly sought after for both the home and export market. Old bucolic films show peasants happily scything their way through chest-high corn. Today’s malting varieties have short stiff straws to withstand the battering from winds; they are bred for increased disease resistance and producing yields that can be as high as eight tonnes per hectare.

Barley for malting needs to have a low nitrogen content as excess protein in a fixed corn size reduces the amount of sugar available for the brewer and can encourage later hazes in beer especially with the current trends for lower serving temperatures. Malts for cask beers that are packaged straight after fermentation should be less than 10% protein, beers that are conditioned or further processed in the brewery can be as high as 12%. Barleys above this level are used for animal feeding. Farmers are paid a premium to withhold fertiliser to ensure a lower protein level but this is at the expense of yield.

Good quality malting barley is grown on the lighter free-draining soils in the east of the UK. Bordeaux wine buffs wax lyrical about terrior which is the interaction between soil and microclimate. Britain has its own such conditions on the barley lands of high Norfolk and near the coast of eastern Scotland where sea frets drift in during most afternoons in summer and keep the barley ears from drying out.

Barley can be sown in winter or spring and malting barley types include Venture, Flagon and Pearl (winters) and Propino, Concerto and Planet (springs). Some brewers swear by old varieties such as Maris Otter and Golden Promise and have to get them grown under contract at a high premium.

In the maltings

barley is aerated during steeping
The barley is aerated during steeping and then emptied to the germination vessels.

Barley arriving at the maltings will be sieved to remove any small corns or bits of stalk and dried to ensure it will keep until it is needed for malting. The first stage is steeping which involves soaking the grain in water which mimics the corn getting wet in the field. Periodically the water will be drawn off and the barley air rested, again to mimic field conditions where the grain has access to the air. After two days it has picked up over 40% moisture and the corns will start to show growth of rootlets. The barley is moved to a germination vessel where cooled humidified air is passed through the grain bed to provide oxygen for respiration and keep the barley cool. The corns are mechanically turned to prevent the rootlets from matting together which would otherwise impede vital air flow.

450t germination vessels
Three of six 450t germination vessels at Great Falls. On the right the vessel is being filled at the Malting Co of Ireland plant near Cork.

Germination takes three or four days to make sure the activation of the enzymes is complete right to the end of the corn. The maltster calls this ‘modification’. The ‘green’ malt is then heated in a kiln, gently at first to evaporate the water without destroying the important enzymes. As the moisture drops the air can be recirculated to save energy and then the temperature is increased to cure the malt producing colour and flavour components. Kilning takes 24 to 36 hours; lager malt needs a shorter time as the required colour is lower. Longer kilning at higher temperatures yields ale malt with darker colours and more intense malty flavours. Malt for grain whisky production is not dried so much in order to provide more enzymic power to convert the added unmalted maize or wheat.

A roasting drum
A roasting drum at Joe White’s old plant at Delacombe in Australia.

Speciality malts for beer brewing can be made by roasting ale malts in drums to produce amber, brown, chocolate and then black malt depending on the temperature reached. At the end of the roasting, the product in the drum needs to be quenched with cold water at just the right time to prevent the whole lot catching fire! Other flavoured malts are produced by raising the temperature while the corns are still wet. The enzymes convert starch to sugar and then caramelise to make Munich, Vienna, carapils and crystal malts as time and temperature increase. Darker malts add colour to milds, porters and stouts while the crystal family add a chestnut colour to beer and a strong malty taste.

Floor malting – old buildings at the Donnington Brewery in the Cotswolds and at Marston’s now closed plant at Lichfield.

The traditional view of a maltings is a long low building with small windows and a distinctive cowl above the kilns at one end. Here the malt was produced on floors and was spread thinly to control the temperature and turned regularly by hand to keep the rootlets apart. The last floor maltings was built in Grimsby, Lincolnshire in 1952 and at the start of the 21st century only a handful are still in use. Commercial operations continue at Crisps, Great Ryburgh in Norfolk, Fawcetts at Castleford in Yorkshire and Warminster in Wiltshire. A number of Scottish distillers are still floor malting including Balvenie, Highland Park, Kilchoman, Laphroaig and Springbank.

Floors have given way to pneumatic maltings where the barley is germinated in much larger quantities in vessels with forced airflow and mechanical turners. Batch size is limited by the size of vessel and a maximum depth of grain at around 1.7m as deeper than this needs a lot more energy to push the air through the bed or ‘piece’ as the maltster calls it.

germination boxes
Open germination boxes at Pilsner Urquell in the Czech Republic and one at Munton’s at Stowmarket, after filling it is awaiting levelling by a passage of the turners. On the right are four malting drums at Cascade in Tasmania where the malt is turned by rotating the drum.

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