Baffled by yeast

A very excited friend posted me this the other day:

‘Yeast!’ she cried, electronically. ‘Geek out!’

It did look interesting. Exciting even, though as someone who wasn’t allowed to even take science at school, I found much of it impenetrable. My esteemed colleague Mr Woodard ventured that Oxaloacetate was in Mexico. Come to think of it, I’m sure I have a mezcal from there.

Anyway, she sent it because she’s been on a distilling course – obviously quite an advanced one because, any time you go around a Scottish distillery and it gets to the yeast bit, the talk goes something like this: ‘Then we add yeast.’

Actually, there’s often less said about fermentation than there is about distillation, but that’s yet another thing to leave hanging up there on the rafters to pluck down at a future date.

It’s always intrigued me why this is the case because, when talking to winemakers or brewers, you almost have to shut them up about yeast because you want to get on with the tour. For them, yeast is an active participant in specific flavour creation, one way to help differentiate your wine/beer from your competitors’. 

The same conversation is to be had at many rum distilleries, when you talk about Tequila, cachaça and mezcal (which tends to be wild ferment). In other words, it matters.

Not so in Scotch. ‘We don’t believe the yeast itself contributes to the final distillery character’ is the line, which means that, since all distilleries use the same yeast strain, the flavour differences which do exist are not generated by the yeast, but by other factors (peating, mashing, fermentation times, still utilisation, cut points).

Actually, looking at that you begin to wonder whether they have a point. If there are so many other flavour-creating opportunities, what’s the point of adding another on top?

But what about American whiskey? What about, for example, Four Roses using five different strains on two mashbills to create 10 different new makes – floral, fruity, spicy, vegetal?

Ah, but, surely after maturation the differences are evened out? No. They remain distinct, even after spending time in new wood. Four Roses might take it to the extreme, but all the other distilleries in Kentucky and Tennessee have their own strain(s).

In Japan, Nikka coyly says it uses ‘around five strains’; Suntory, too, has a selection of different yeasts for its makes. 

It used to be the same in Scotland when distillers used a mix of distiller’s and brewer’s yeasts. This stopped when local breweries closed, lager rather than ale yeasts were used and the Scotch industry was looking at ever greater efficiencies.

Will things change? It is interesting to observe how many of the new whiskey distillers in the States are coming from a craft beer background where different roasts of barley and yeast strains are the norm. These learnings are now being applied to their whiskies. David Fitt at English Whisky Co – an ex brewer – is doing the same, as is Darren Rook at the London Distillery.

There might be an ‘if it ain’t broke’ attitude in Scotland, it could be that a switch to multiple yeast strains is difficult to retrofit, or their introduction might cause cross-contamination.

Maybe it’s a bit like the law: easy to change, but difficult to undo once the change has taken place. I do know one of the bigger distillers is looking into yeast, but they are an exception. If I was a new distiller it is one area I’d be looking at.

But I'm not a distiller, or a scientist. Maybe that’s why I remain somewhat baffled.