Barley is single malt whisky’s primary ingredient — the source of its complex flavour. Quite simply, without this seemingly humble grass there would be no casks filling warehouses the world over, no single malt industry, no Waterford Whisky.

The law states single malt whisky has to be made from  ‘barley, yeast and water’ alone, but barley, the primary source of whisky’s very essence, we feel is under-discussed. Certainly by comparison with the raw materials that make up other drinks — like wine. 

So let’s talk barley. In fact, let’s talk barley properly, with one of the foremost barley experts in the world, the American scientist Dr Dustin Herb. Dustin, working at the University of Oregon,  has been key to establishing that the terroir of barley directly affects the resultant flavours of whisky (peer-reviewed terroir) and his current research is at the heart of the Journey Project, unlocking the potential of historic heritage barley to create new varieties based on flavour. In short, there’s no one better to offer a barley 101. The floor’s yours, Dustin…

Tell us about barley as a plant and what makes it a good fit for whisky.

Barley’s one of the more ancient of the small-grained cereals. It originated in the Fertile Crescent and it’s been a hugely important crop not solely within the alcohol industry but also within the food industry for the longest time. 

It’s persistent in our culture — that’s what’s inspired a lot of people to conduct research — and it’s emerged more within the beer or whisky industry. But it still has implications within feed and food consumption. It depends on the culture. 

And because of these factors, there’s been a lot of work on barley. It’s a diploid species, so it has one genome. This makes it a very simple crop to work on and study genetics with — so it’s become a model species for a lot of genetic studies in pathways and metabolomics. As a plant there’s variation within the species and there are also sub-species within barley. It’s interrelated to other small-grained cereals. It can be two-row, which means that it has a seed on either side of the spike, and it can also be six-row which means that it has three seeds on either side of the spike. 

There are also winter and spring varieties, and that really changes the flexibility of the plant, changes its yield, and allows people to avoid certain disease pressures. There’s also, between two-row and six-row, different implications. Europe uses almost entirely two-row barley because it has a plumper seed and so you get more extract out of it. It yields better because it’s bigger. But six-row is still sometimes used, especially in macro-breweries for adjunct brewing, because it’s very high in enzymes — it’s intrinsically higher in enzymatic power, which allows it to malt well. Those enzymes, when they’re in the mash, can then move through the mash into other grains that are unmalted — with low enzymes — and actually start converting that starch into sugar. 

Barley is a very good crop — there are no other small-grain cereals that have the same enzyme power. That’s why it’s become this powerhouse in the whisky industry. It’s economically viable for growers, it’s good for crop rotations, there are multiple different industries that take barley as a crop, all of which gives a lot of flexibility for the consumer and for the grower. 

That’s especially the case when inventory’s long and price of seed goes up or down. It’s important in brewing and beer, and has maintained its position essentially because of its enzyme power.  It’s possible to source starch from other areas, but barley has the intrinsic enzymes and responds really well in the malthouse. 

Having a hull, an outer layer, the husk still on there that’s ‘adhered’ to the kernal,  [means that] when you malt it, it’d become softer. Then when you milled it, it allowed for the hull to come off, but stay attached. That hull would allow a layer of filtration if you were lautering through your traditional mash tun and then sparging back on top of it; creating that grain bed allows you to pull off clean wort. It acts as a net to catch denatured proteins and small particles from the grain and so you can access a cleaner wort. 

This was a natural part of the grain that could be capitalised on for the malt production process. So having an ‘adhered hull’ and those enzymes are, in my opinion, the two biggest factors for its importance in brewing. 

Outside of that, it yields well, it’s a very easy crop to grow. It doesn’t really take a lot of convincing to get farmers to grow barley – especially when they can use it as a rotation crop for more valuable plants – because barley as a whole is not the cash crop that farmers are looking for. There are limited subsidies from governments, if any, on the crop and it doesn’t yield as much as some of the other cereal grains. But it does offer a pretty consistent market, and so a lot of the time prices stay fairly static within barley – malting barley is not a commodity-traded product, so the price doesn’t fluctuate like it does with wheat. 

The situation we have right now with Ukraine being a massive exporter of wheat and 20% of the world’s barley, since the war we’re now seeing they’re not sowing,  harvests are rotting,  storage is maximised, so there’s no room for the latest harvests and crops are being hijacked or destroyed — this food supply is going to be coming out of other countries, the price of cereals has doubled in the last couple of months. In addition, there is the increased cost of shipping, fuel and fertiliser cost as well as associated production costs such as energy. Barley, compared to wheat, is a more stable economic unit ideally suited to the brewing process.

You’ve said that barley is reasonably happy to grow anywhere, but what does it really like? What would be the ideal growing conditions for barley as we would want it for whisky?

Barley can handle a wide range of production environments. And that’s the work of plant breeders who have, for centuries now, been moving varieties outside of its original area. Coming from the Fertile Crescent area, barley grows well in semi-arid places. Arid’s fine —barley can handle not having that much water.  

That doesn’t mean that it’s the optimum for production though — temperate conditions, plenty of water, dry summers, especially when ‘heading’ is the best. Temperate climates — 62–72 degrees Fahrenheit (16–22 Celsius), that nice middle range very similar to Ireland at this time of year, where there is a decent amount of rainfall so you don’t have to irrigate it. It grows very well in areas that are semi-arid, but have the potential for irrigation, because you have all the heat units that are needed to grow a nice, fuller, stronger plant. 

Good soil nutrients are important — part of that goes to proper management of the fields. But there are some areas that will have intrinsically low pH, some areas have a high pH and that changes the nutrient availability. This doesn’t mean that you can’t grow in those areas, it’s just not such an optimum range. 

An interesting fact about barley is that in a lot of areas with dry summers you don’t need to have seed dormancy. When the barley is harvested in Ireland it has to be stored — for Waterford it goes to the Cathedral. That’s not just for staging before it gets to the malthouse and then brewhouse, it’s because the barley has to sit for a while and allow that dormancy to actually break within the seed itself. Because Ireland has wetter summers with intermittent rains, if that seed didn’t have dormancy, when the later seeds are drying on the spike and ready to harvest, if you’re just not ready to harvest it yet and the rains come in, it has such good enzyme power that it can actually start germinating  in the head itself. You would see  a secondary growth on top of the spike. 

And that means its no longer good for the malthouse because  you’d probably  destroy it; besides  you’d have less gibberellic acid to initiate full germination again — it’s already expended what it had. That’s called pre-harvest sprouting. And all of Ireland and the UK, and everywhere east of the Rocky Mountains in the US has this issue, so seed dormancy counters that. Where I’m from in Oregon we have pretty dry summers, which allows the seed to actually get to flowering and to produce all that it needs to go to pre-production, and then dry down quickly. 

The weather heats up, the wind blows, it pulls all that moisture out and it makes very high-quality seed. Whereas if you let it sit and get weathered it gets dirty-looking. West of the Rockies we actually breed our varieties to not have seed dormancy. And what that allows us to do is harvest the grain and go directly into the malthouse. We don’t have to hold it to break dormancy — it can immediately be used up by the malthouse; that’s why we have a lot of malthouses in the Idaho area, Western Montana. It’s a really good spot for producing. But that seed dormancy is a natural trigger that allows barley to be grown in so many other different climates.

How have we arrived at modern barley varieties — what have they been bred for?

Modern varieties have been developed for broad adaptation and for consistency. August Busch, the founder of Anheuser-Busch, would bring many barleys in to his tasting programme. His sensory room wasn’t for flavour, it was for consistency. 

He wanted the same consistent product year after year, batch after batch, every single time. So that informed, for at least North America and I would imagine for the rest of the world, how barley was developed for the next 100–150 years, until we start talking about – wait for it – flavour. But that doesn’t mean that the varieties don’t have flavour, it just means they were bred for neutral, consistent flavour that’s not going to interfere with the other flavours being added during the  process, like hops. For the Waterford Terroir Project the varieties we used were what was commercially available, decided by the big brewers and distillers.

Waterford can’t go to its growers and ask them to sow specific barley varieties. Varieties have to be on an Irish national registry and then they have to be placed in contract, so there are legal things that tie up what can be done. The varieties were what Minch Malt was placing contracts for at the time. We didn’t think anything of it, but when I saw there wasn’t a huge variety effect I contacted a barley researcher, a colleague of mine, Dr Bill Thomas, from the James Hutton institute in Scotland, and asked him, ‘Can you do a little dive into these two varieties?’ Because they’re not public, they’re private varieties — but there’s a lot of information. He discovered what all the parents were and found out that the two varieties are actually within one generation removed from each other. So they share basically the same genetics there’s very little difference between those varieties. They share one wing — while they’re not sister lines there’s no real difference genetically between them. It’s hard when you want to test for difference in flavour. It’s not like testing which beer tastes better — this recipe or that  ingredient? Which could have drastically different impacts on flavour.

The flavours here are so small that it takes a highly trained panel to pull them out, and you have to have huge numbers of samples to have the panel detect these small differences. We can’t do it like that because it’s got to be sown, grown, harvested, stored, malted, brewed, distilled and then sensory tested with the team. We were saying ‘listen, we’ve found a few differences in varieties, but they were insignificant  and weren’t as widespread as environment — the terroir — because they were too genetically similar.’  We needed to move forward and say ‘let’s create something that IS different; let’s get some genetic diversity out here and let’s see what those flavour differences are really going to be.’