Why do we use barley to make single malt Scotch whisky?
Firm and crunchy, yellow in appearance and with a slight nutty taste…no, we aren’t talking about our latest whisky release. We are actually talking about the humble grain at the heart of the whisky production process: barley. If you’ve ever thought, “Why barley?”, then you’ve come to the right place to find out.
Why barley?
Why do we use barley to make whisky, especially Scotch whisky?
Quite simply, barley is amazing; all the processes that go on inside every single barley grain on a molecular level make whisky production possible. And it’s a process that dates back hundreds of years. Even as far back as 1494, Friar John Cor was instructed to buy “8 bolls of molt for the production of aquaviate”. Everything in this sentence (the unit of weight and the name of the end product) has changed except, beyond the spelling, the key ingredient: malted barley.
Barley has (always had) the right combination of physical attributes, process-ability, enzyme content and flavour potential to be the “Rolls-Royce” of spirit-producing grains. And the unsung heroes are the enzymes that are present in the barley. These are proteins that make the barley’s starch available and convert it to fermentable sugar.
In the production of Scotch whisky, the law does not permit the use of additional enzymes – something that doesn’t apply to Irish whiskey or grain distilling outside of Scotland. To make single malt Scotch whisky, we have to make do with the barley’s own internal or “endogenous” enzymes - fortunately, these are more than capable of converting the long chain starches to sugars which yeast can consume.
Here’s a quick overview of what takes place
- Steeping: Barley grains are steeped in water, allowing them to absorb moisture and begin to germinate.
- Germination: As the barley sprouts, it naturally produces enzymes. The most important of these for whisky production are amylase enzymes.
- Kilning: After a few days, the germination is halted by drying the barley in a kiln. This dried, germinated barley is now called "malt."
Amylase enzymes are absolutely crucial because they are the key to converting complex starches within the barley into simpler, fermentable sugars. Without this conversion, yeast wouldn't have anything to feed on, and fermentation – the process that creates alcohol – simply couldn't happen effectively. While other grains contain starch, barley's high enzyme content, particularly after malting, makes it incredibly efficient at this conversion.
At Lagg, we use 100% Scottish barley. Most of that comes from the east coast of mainland Scotland, but for a few weeks of the year we create new make spirit with barley grown on the island a stone’s throw from the distillery.
The prevalent strain we use is Laureate - a versatile spring malting barley. We mash 4 tonnes of malt per batch and currently do 5 mashes per week. It’s performing well, giving us a predicted spirit yield (PSY) of roughly 410 litres of alcohol per tonne.
The structure of a barley grain
*Image: Barley grain structure - Journal of the Institute of Brewing / CC BY 4.0
This image shows the structure of a barley grain, and each of these parts plays a role in producing the golden dram that we know and love.
Germ
The source of the root and shoot for a new barley plant. This is also the starting point of the chemical chain reaction in the malting process. When we steep the barley to raise the water content to 45% then lay it on a warm malting floor, the magic happens. Gibberillic acid is released by the embryo, which causes the aleurone layer to wake up and get to work! The germ and embryo would be the start of a new plant…if we didn’t interfere!
Aleurone layer
The enzyme creation powerhouse of the barley grain. In response to the embryo’s Gibberillic acid, beta-glucan, alpha and beta amylase (required in mashing), and other enzymes are secreted into the endosperm, which is the main body of the barley grain.
Endosperm
The main body of the barley grain, this contains the grain’s “food” reserve which, in nature, would sustain the initial growth of a new barley plant.
Cell walls
These are gum/sugar/protein walls surrounding the precious starch granules held up in the protein matrix. They are broken down by the aleurone-layer released enzymes to expose the granules to enzymes for conversion. Broadly speaking, the more granules, the thinner the cell walls. Modern barley breeders manipulate these attributes to maximise the potential for distillers.
Protein matrix
The ‘glue’ that suspends the starch granules. It too is broken down by aleurone-layer produced enzymes. The best analogy here is Toblerone, where the chocolate is the protein matrix and the nutty bits are the starch granules. If you sucked a piece of Toblerone, your mouth (the enzymes) would heat the chocolate (protein matrix), which would melt (break down), exposing the nutty bits (starch granules).
This breakdown is the production of the “food” that the baby barley plant would need to grow itself above ground before beginning photosynthesis.
Husk
A very important part of the barley plant to a distiller. Not chemically exciting, but it is of the utmost importance in helping us attain good drainage through our mash-tun. Pairing the husk with a properly set mill can be the difference between a successful mash with high extraction or making yourself 15,000 litres of porridge. Yum.
Flavour contribution
Beyond its enzymatic superpowers, barley also plays a significant role in shaping the flavour of the final whisky.
Nutty and cereal notes
The malted barley itself contributes a distinct cereal character to the new make spirit, often described as biscuity, nutty, or grainy. These foundational notes provide a canvas on which other flavours develop during fermentation and maturation.
Variety (to a degree)
While less pronounced than using different grapes to make wine, a specific variety of barley and the conditions in which it's grown can subtly influence the whisky's character. A poor quality barley can affect the ratios in the mashing stage.
Peat
For peated Scotch whiskies, such as the ones we make here at Lagg Distillery, it's the malted barley that is exposed to peat smoke during the kilning process. The phenols from the smoke adhere to the barley, imparting aromatic compounds.
Where the peat comes from can affect the smokiness of the whisky. For example, Islay peat, rich in seaweed and maritime vegetation, often gives whiskies a medicinal, briny, and iodine-like character. In contrast, we use Highland peat - typically derived from more inland plantlife like heather and forest material - which produces a gentler, earthier smokiness.
So, the next time you look at a bottle of whisky, you can give an appreciative nod to the contribution this little grain makes. Speaking of which, why not check out our range of single malt peated whiskies - a delicious clash of contrasts with every sip. Or book a tour of our distillery and join us for a deep-dive into the whisky making process.