When I visited Scotland last Spring, I discovered many things, among which the fact that I was hooked to whisky forever.
That being said, one of the nice hobby I also have is brewing beer.
Brewing beer is a very time consuming yet rewarding hobby. The fun part for me was as much in brewing it and tasting it as it was in setting up my gear, tinkering with the toys, so to speak.
But one should never forget that beer is, after all, baby whisky. It comes from malt, water and yeast and might or might not be matured in a barrel. Essentially, though, it’s the same product initially.
One of the things that fascinated me the most when I started brewing was that it’s extremely surprising how two beers could be very different just by changing the yeast. There’s a wide range of commercially available yeast these days: dry or liquid, saccharomyces cerevisiae or brettanomyces, and among these, even more diversity when it comes to yeast having been selected over – sometimes – millenia by happy brewers.
Weihenstephan for instance is a well known Bavarian brewery which has selected and kept their yeast for a very, very long while. A hefeweizen and a doppelbock might not have the same grain bill, but they also do not share the same yeast.
But why would they? They’re two different products. When you cook yourself a nice fruit salad, you’ll probably go for sugar and not salt. The reason for that is that it’s more commonly appropriate to associate fruits with sweets as it’ll bring out some tastes and sensory experiences you would not have otherwise.
Yeast is kind of the same: it’s an essential part of what makes beer, well, beer.
So what is yeast anyways?
Yeast is a microorganism of the fungus kingdom which will metabolise sugar in order to transform them, among other things, in alcohol (yay!). Yeast does that by, based on the results of the enzymatic activity during mashing where long chains of sugar are transformed into simpler chains of sugar, metabolising these sugars into alcohol, along with by-products including a magical thing called esters. We’ll come back to that later.
But it’s not as easy as it sounds: yeast has constraints. It can be temperature, where some typical lager yeast produce more desirable things at lower temperatures, as opposed to ales or even kveik – the latter being the kind of yeast that can live with heat; it can be length of fermentation, as some strains of yeast require more time to eat all sugars, or even total amount of sugar present in the wort to ferment.
Yeast also produces by-products while fermenting. Some can be undesirable. For instance, diacetyl gives a notable buttery taste to the final product. To avoid having it, a number of steps can be taken, one of which being having a longer fermentation time at a slightly higher temperature by the end of fermentation (this is called a diacetyl rest).
Some are highly desirable – the esters. They participate to the actual flavour of beer and can give taste and sensory experiences ranging from fruity to solventy, going through the range of flavours. It’s generally accepted that the fruity aromas you might perceive are a typical thing produced by esters issuing from yeast fermentation (but not necessarily – hops play a role too!). They’re due to a reaction of organic compounds in the wort (which composition thus has an influence on the final result as expected) and the alcohol produced by the fermentation itself. We can most commonly link them to banana, pear drop, apple, honey, roses…
Stop ranting about beer you idiot and bring whisky in already
So how does that apply to whisky you might ask?
Well, whisky is beer for grown-ups, after all. Isn’t it? When whisky’s chill filtered, esters are mostly removed from our preferred beverage. The effect of that filtration is, in effect, to remove most of the nice complexity which makes it whisky. Dr. Heinz Weinberger calls esters the stars of the whisky world for a reason: they bring out flavours and olfactory experiences you would not have without them.
This is why we see a rise in demand for non chill filtered whiskies, for which one of the most vocal advocates are independent bottlers. Much similar to the rise of IPAs and craft beers, non chill-filtered whiskies are in demand for a different, some might say more authentic, experience.
So why talk about yeast then instead of esters?
Well if you remember the beginning of this post, the activity of yeast is what produces esters. It produces it given time and proper temperature.
Temperature is a thing that is monitored in distilleries but which can range widely. In winter, it might drop, in summer, it might be going higher than expected. This has an effect on the length of fermentation which in turn has an effect on ester production.
Considering that sheer influence of yeast on whisky, then a question comes to mind very clearly.
Why would distilleries ferment very fast and with distiller’s yeast?
As stated earlier, the strain of yeast has a tremendous effect on beer. For instance, hefeweizen yeast will traditionally bring out bananas or cloves. So when I visited distilleries this Spring I asked around these two simple questions:
How long do you ferment your wort for?
What kind of yeast are you using?
To my surprise, most of them use dry distiller’s yeast. This type of yeast is usually optimised for conservation (it’s dry so less “fragile” and easier to handle) and alcohol production (it can eat out more sugars to produce more alcohol in less time, basically). It’s easy to understand the appeal of such a thing: you do not have to maintain a “yeast bank” or any kind of liquid repository of yeast, it’s less subject to yeast going to a dormant state and then dying (which might lead to least autolysis which isn’t desirable either), and as it ferments faster and more completely, it’s far more comfortable on a production schedule.
On top of that choice of dry yeast, they also tend to ferment between 50 to 70 hours. This gives plenty of time for yeast to eat the sugars, but this will not necessarily mean that the yeast will eat its own by-products and give enough time so that chemical reactions happen to produce the so much desired esters.
Fermentation time also wildly varies between distilleries, and that is not even mentioning fermentation vessels (stainless, wooden…). When seeing the standardisation of distilling practices, considering the stills and practices are kind of similar across distilleries, one could ask the following question.
Is anyone doing different things?
Let us rejoice that yes, the world is changing, there’s more demand for whisky and more knowledge about it, driving for more diversity in maturing, finishes and… yeast!
Glenmorangie’s Allta is a good example as it was fermented using a wild yeast strain, giving it a notable difference when compared to what Glenmorangie usually does. Is it better or worse? That’s for you to judge, but it’s a change as compared to the industrial ways according to which whisky’s made these days. I personally appreciated it and I own a bottle.
I’ve also heard on the grapevine that some distilleries are using longer fermentation time. Benromach, for instance, ferments between 60 and 120 hours and according to Brian’s Malt Musings, Loch Lomond is also aiming for longer fermentation times.
Nothing here is really new. As a matter of fact, while researching for this article I stumbled upon a very nice piece from Jordan who outlines exactly the same point as I do, albeit going through more technical details that I didn’t think were appropriate on this blog.
I do hope the future is holding much more surprises for us as some are leading the way. Plus, with the explosion of craft brewing, yeast is following through too. It’s not that difficult to get your hands on some odd yeast, including as mentioned before some kveik strains which have been around for a while. So stay tuned for more innovations which will end up, as always, in our glasses.