Why Barley?
David Hsieh
The four physical facts behind Scotch single malt — from starch, husk and enzyme, through a delivery note and a single PSY figure, to what actually drives a distiller’s choice of grain
By David Hsieh — Master Distiller, Tankyu Distillery | Presenter, Business Whisky Guide Podcast
Adapted from Business Whisky Guide Podcast EP2 — ‘It’s barley, not wheat!’, recorded in Scotland, February 2023.
The choice of grain in whisky is usually presented as a matter that needs no explanation: Scotland has used barley for centuries, the tradition continued, here we are. From a distiller’s point of view, the story is less romantic — and rather more interesting. Barley sits at the heart of Scotch single malt because it happens to combine four physical advantages that no other common grain offers simultaneously.
What ‘Scotch single malt’ actually means in law
Each of the four words is precisely defined. ‘Scotch’ means the spirit must be distilled in Scotland and matured there for at least three years. ‘Single’ does not refer to grain variety, or to vintage; it refers to a single distillery. ‘Malt’ is the critical word: the raw material must be one hundred per cent malted barley, and the distillation must be in copper pot stills, in batches.
Use a column still or a hybrid arrangement, and even if the grain is still barley, the law obliges you to label the spirit as Single Grain Whisky. The identity ‘single malt’ is therefore locked in by three separate rules — raw material, equipment and process — operating in concert.
Which brings the awkward question into focus. Of all the grains a distiller might choose, why barley?
Four conditions that put barley ahead
From the distiller’s bench rather than the marketing brochure, barley is the principal grain in Scotch because it carries the following four properties at once.
One — starch content is high. Barley runs at roughly 58 to 65 per cent starch, ahead of wheat and ahead of oats. Starch is the feedstock for mashing, and the more starch you put in, the more sugar you can convert and the more alcohol you eventually distil out.
Two — the husk gives a natural filter bed. When barley is milled and mashed, the husks settle to the bottom of the mash tun and form a filter layer that allows the wort to run off clear, without blocking the downstream pipework. Strip away the husk and the whole mashing system becomes considerably more troublesome to operate.
Three — the gelatinisation temperature is low. Barley starch gelatinises between roughly 60 and 70°C, which is well within the range of the hot water used in an ordinary mash tun. By comparison, maize and rice gelatinise at 90 to 100°C and have to be cooked under pressure before they can even enter the mashing step.
Four — the malted grain carries its own enzymes, in abundance. Malted barley contains enough diastatic enzyme not only to convert its own starch into fermentable sugar, but to convert the starch of other grains as well. A standard grain-whisky recipe might run at 50 per cent maize, 30 per cent wheat and 20 per cent malted barley, and that 20 per cent of barley supplies enough enzyme to drive the entire mash. Take away the barley and the whole system is left without its chemical key.
How distilleries actually buy malt: one delivery note and one PSY number
Inside an operating distillery, the way malt is chosen has very little of the language of terroir or grain variety about it.
The reality is that the great majority of Scotch distilleries do not malt their own barley. They buy in finished kilned malt from professional maltsters. What turns up at the receiving bay is, in many cases, a single delivery note that records tonnage and variety, and very little besides.
The figure that actually drives the purchasing decision is Predicted Spirit Yield — PSY — typically expressed in litres of pure alcohol per tonne of barley (LPA/tonne). The working threshold for a modern Scotch distillery is 400 LPA/tonne, with the current mainstream varieties — Concerto and Laureate among them — reliably clearing 420 LPA/tonne. A variety that falls short of PSY rarely makes it through the front gate of a large distillery, however well it may be remembered.
Golden Promise — and a different way of looking at ‘revival’
Of the older barley varieties, the name most often invoked is Golden Promise, the dominant grain in Scotch from the 1960s to the 1980s. Its spirit yield is around 350 to 370 LPA per tonne — by today’s standards, low — but the historical aura is considerable, and one or two smaller distilleries have recently contracted growers to bring it back, on the strength of a ‘revival’ or terroir story.
From a distiller’s point of view, the proposition ‘use the old grain, recover the old flavour’ deserves to be examined rather more carefully than it usually is. The flavour of those earlier whiskies was not the product of the barley alone. Yeast strains, the geometry of the still, the provenance of the casks, the climate during maturation — every one of these variables has moved on over the decades. Replant Golden Promise as faithfully as you like, and the spirit that comes off the still is still very unlikely to taste of the 1970s.
The grain, in other words, is one variable in a much larger system.
What may be worth looking back for is the gene, not the flavour
Is it then worth studying these old varieties at all? It may be — but for a different reason.
Older varieties were displaced largely because of their weaknesses: poor disease resistance, unstable yield, susceptibility to weather. Yet in an era of climate disruption and monoculture, agricultural scientists are taking a fresh interest in those same older grains — precisely because of the adaptations they accumulated over centuries of facing drought, damp, cold and disease. That stock of inherited resilience is, in itself, a useful resource for modern breeding.
Looking back at Golden Promise, and at older varieties still such as Chevalier, the genuine value may not be the recovery of an old flavour but the recovery of useful genes — traits that could make tomorrow’s barley more stable, and more equal to a more extreme climate. For an industry whose principal raw material is time, that is the direction worth the long view.
About the author
David Hsieh is master distiller at Tankyu Distillery. He has previously worked as a distiller at several whisky distilleries in Scotland. He holds an MSc in Brewing and Distilling from Heriot-Watt University, and is the host and producer of the Business Whisky Guide podcast, the most popular whisky podcast in Taiwan.
Source
・ Business Whisky Guide podcast EP2 — ‘It’s barley, not wheat!’, recorded in Scotland, February 2023. Original audio: youtu.be/yeC6Vm0r-6o