FLAVOUR FOCUS
Mad about the malt
Once a distillery has decided what variety of barley it will be using, the humble grain has to be malted before it can germinate and ultimately produce a range of aromas and flavours that carry through to the whisky in your glass. Gavin D Smith explains how that happens, and how malting can influence flavour
The practice of malting is essential to the production of malt whisky, as barley must be processed to allow for the creation of alcohol. Each barley seed comprises an embryo – the part that will grow into a new plant – and the endosperm, which contains starch to feed that plant.
The starch cells are held in a matrix, divided by protein walls, and enzymes that break down those walls to make the starch available for growth are produced during germination. Other enzymes are also stimulated, and they convert the starch into soluble dextrin and ultimately into the soluble sugar maltose.
The process of malting effectively involves a ‘con trick’, fooling the barley into thinking that spring has sprung, causing it to commence germination. During malting, germination is allowed to continue until the point where the cell walls have been breached, but before the starch is consumed by the plant. Germination of the ‘green malt’, as it is known at this point, is halted by drying the grain in a kiln.
The initial stage of malting involves ‘steeping’ the barley in water to activate the enzymes that will ultimately enable alcohol to be produced. While submerged in water, the barley is aerated to provide consistency of hydration, and the grain undergoes periods of immersion and air rest over a period of two to three days.
ABOVE: barley steeping
ABOVE: barley mid-germination with rootlets showing
After steeping, germination is allowed to proceed for four to five days, and in old-school floor maltings which were once found in every malt whisky distillery, the moist barley is spread out on a concrete floor, and the grain begins to sprout rootlets.
Heat is generated within the ‘piece’, as the bed of barley is known, so it must be turned regularly on a 24-hour basis to maintain an even temperature and prevent entanglement of roots. Traditionally, wooden shovels or ‘shiels’ were used to turn the piece, but motorised shovels are now used in most of the distilleries that operate floor maltings. William Grant’s popular blended malt Monkey Shoulder is named after the temporary ailment that affected maltmen as a result of turning the piece for several hours at a time. The hard labour would cause a shoulder to hang, rather like that of a chimpanzee, as described by author Neil M Gunn in his book Whisky & Scotland, first published in 1935:
“…the maltmen have continued at regular intervals to scatter the grain in showers with rhythmical sweeps of their wooden shovels – an attractive sight to watch, and one that has always been to me, for some obscure reason, a little foreign, as though it belonged more rightly to the great barns of the granaries of a Europe still with the rhythm in its labour of the mediaeval age. But despite all the Gaelic labour tunes behind them, these maltmen do not sing at their work – possibly for the same reason as prompts the reader to smile at the thought of it in this commercial age.”
“Monkey Shoulder is named after the temporary ailment that affected maltmen as a result of turning the piece for several hours at a time. The hard labour would cause a shoulder to hang, rather like that of a chimpanzee”
The germination process lasts for up to a week, with ‘modification’ occurring as the grains are gradually spread more thinly on the malting floor until the rootlets start to wither and the ‘green malt’ as it is now known takes on a mealy quality. Neil Gunn describes how it was determined when germination had proceeded as far as was desirable. “As the old maltman put it ‘When you can write your name on the wall with it (the ear), it’s ready.’”
The next stage of malting is referred to as kilning, which stops growth in the green malt by drying it to a moisture level of around 4.5 per cent. The grain is placed in a kiln, where it is spread across a perforated metal floor, with a heat source below. The initial ‘free drying’ phase of kilning requires initial temperatures no higher than 55-65°C in order not to damage the all-important enzymes that will later convert starch to sugar.
ABOVE: Today, pneumatic maltings are responsible for supplying the vast majority of malt
It is during the ‘free drying’ process that another flavour variable may be thrown into the mix, courtesy of the use of peat in the furnace. When peat is employed, the phenols in its make-up – which are responsible for smoky aromas and flavours – only adhere to damp green malt, and the lower the temperature, the higher the level of peatiness (recorded as phenolic parts per million, or ppm, imparted).
Not all peat is the same in terms of the characteristics it gives to malt, with Islay peat, for example, delivering medicinal, maritime notes, while peat from the middle of Aberdeenshire will be altogether more earthy and lacking in those notes of antiseptic TCP and Germolene cream so beloved by peat-heads. Back in Unfiltered issue 41, in 2018, we looked into the science of how peat differs from various regions – and put some Society members to the test to see if they could perceive the differences in their drams.
“Not all peat is the same in terms of the characteristics it gives to malt, with Islay peat, for example, delivering medicinal, maritime notes, while peat from the middle of Aberdeenshire will be altogether more earthy”
The initial ‘free drying’ phase of malting is followed by ‘forced drying’, in which temperatures are raised to between 70°C-75°C and the flow of air is reduced, leading to a moisture content of around five per cent. Overall, the kilning process takes from 20 to 48 hours to complete.
So far, we have explored the business of malting in its traditional manner, as carried out at individual distilleries, but the reality is that today, very few distillers operate floor maltings. Back in the 1960s, as global demand for Scotch whisky grew, new distilleries were created and existing ones expanded. The amount of spirit that could be made was constrained by the availability of malt produced on distillery malting floors, and a solution was to construct large-scale, dedicated malting plants to supply the requirements of several distilleries. Not only did this provide greater quantities of malt, but it also removed issues of variability within the malt and the hard manual labour associated with its production.
Today, pneumatic maltings are responsible for supplying the vast majority of malt required by the Scotch whisky industry, often combining all processes in Steep, Germinate and Kilning Vessels, known as SGKVs.
When distilleries such as Balvenie, Glen Garioch, Highland Park, Kilchoman, Laphroaig and Springbank produce their own in-house malt, this usually only accounts for around 20 to 25 per cent of their requirements, with the rest having to be acquired from third-party maltsters.
However large and sophisticated modern malting plants may be, they are performing exactly the same series of functions as their more primitive predecessors, but experimentation and innovation within the malting realm is alive and well.
ABOVE: Dedicated malting plants provide for greater quantities of malt, as well as removing the need for hard manual labour
To take two examples, in 2022, Edinburgh’s Holyrood distillery created a style of malt whisky named Lightly Peated as part of its annual Cask Programme. This was made with heavily peated malt as well as rauch malt, a German malt smoked over beechwood. In the same year, Glenmorangie launched A Tale of the Forest single malt, distilled from barley kilned with woodland botanicals, including juniper berries, birch bark and heather flowers.
ABOVE: malted barley ready for mashing
With malting complete, the next stage of whisky production is mashing, and the manner in which this is undertaken plays a significant part in determining the ultimate spirit character.
In terms of the aroma and flavour characteristics malted barley imparts to whisky, descriptors such as smoky, nutty, chocolate, cereal, toast and even just ‘malt’ may be applied. Check out the Society’s Flavour Profiles chart, which offers a great range of descriptors for whisky that has been ‘peated’ during malting.