Yeast Stress, Temperature, and pH

Learn this core claim: yeast strain alone does not create a flavor profile. Flavor direction comes from yeast + environment, especially temperature and pH (sourness).

Quick summary

Core principle

So we talked about yeast and that it has two metabolisms. We talked about just pitching yeast by sprinkling it on top.

We discussed how much you actually need. Let's dive into the really important question.

It is a question that you can read a lot about, that you can visit workshops for, and I just want to nail it down for you. How does the yeast that I choose influence the flavor of the spirit I'm trying to make?

That is a really important question, right? Because we all know that if we make beer, as a consumer's beer, the choice for the yeast is very, very important to create certain flavors that you want to have in your beer.

Now, if you want to take that beer and distill it into a whiskey, it better has the flavors that we are actually looking for. The problem with this topic is that there's a lot of, let's just say, there's a lot of bullshit out there.

There's a lot of really bad information. And unfortunately, that information comes from people that don't really understand yeast, or even worse, that actually do understand yeast and make a living out of it by selling it to you.

They'll say, this is an amazing yeast because it makes rum really taste very well. Or they'll say, okay, okay, so you want to make a very complex whiskey.

Now, that's the kind of yeast you need to buy. It's like 10 times more expensive than, for example, normal baker's yeast, but you want to make an amazing whiskey, you need an amazing yeast.

Then they start to talk about how fruity the flavors are, or how nice and multidimensional the flavors are, or how good the yeast is at actually consuming all the sugars and turning it into, very effectively so, a lot of alcohol. But there's a layer underneath, and that's the layer I want to talk to you about today.

The layer underneath that is that yeast is a simple organism that lives in an environment, and if we create certain hostilities or a cozy place in that environment, what happens is that that yeast is going to be happier or less happy. It's going to be in a situation where it feels it can do its job perfectly well, or it gets stressed out.

All those stories about different strains of yeast making different flavors boil down to a very simple scheme, which I'm going to draw for you right now. Your fermentation isn't just about water and grain and yeast.

It's about temperature management, and it's about the management of pH, sourness. And any yeast, any yeast strain, let's take distiller's yeast, quite neutral, has the ability to work in a slightly warm environment or a slightly colder environment, and has the ability to work in a slightly more sour environment, or in a more base, a sweeter environment.

How it works in practice

The question about flavor composition and yeast has to do by how far we push the yeast out of its comfort zone. for example this is a neutral yeast. That's why it's sitting in the middle.

For example, we actually ferment at very high temperatures, 30 degrees Celsius and more. We push the yeast outside of its comfort zone. It starts to create other flavors.

What would happen if we would introduce the yeast to a beer fermentation that is actually very sour? We push the yeast outside of the threshold where it normally likes to live and work. As a result, it creates different flavors.

So it's not the yeast that makes certain flavors. It is a certain yeast that makes certain flavors based on the temperature it's comfortable at and the sourness level that you actually do your fermentation at. How does temperature and how does sourness actually affect flavor composition?

The higher the fermentation temperature relative to the yeast you use, the more fruity flavors you get. You will also get a slightly bigger heads contamination. But it's where heads mingle with hearts where you actually find fruity flavors, front of mouth.

So if you want to make a fruit brandy, probably go for a slightly higher temperature of fermentation even when you use a distiller's yeast. By pushing it outside of its comfort zone, we actually create more fruity flavors. Sourness actually works on the third dimension, back of the throat dimension, the rootiness, the earthiness that you find in so many, for example, Jamaican rums or Scottish whiskeys.

The reason that sourness is created is because we introduce the yeast to an environment that's almost hostile to it. It is so sour that as a byproduct, it starts to make flavors, ester molecules, that give it that third dimensional, rooty, earthy flavor. So to summarize, the yeast strain in itself doesn't create certain flavor profiles for you.

It is the selection of a certain yeast and then pushing it into certain directions because you want to manage your fermentation temperature and your fermentation sourness level. And by doing so, you create a very wide spectrum of flavors. If we go for this position, we create a very fruity rum or whiskey, but also a very rooty, nutty, and earthy rum or whiskey.

What if we were making a brandy with brandy, you want the fruitiness, you don't want the rootiness. So probably what you do in your management of your fermentation is you swing back. You may want to have the high temperature because the high temperature actually helps create more fruity flavors, which is totally logical if you want to make a fruit brandy.

If you don't want the rooty and earthiness, make sure you manage your pH. Let it be at around 5.2 instead of 3.5. Making amazing spirits and looking at the role of yeast is not about selecting the right yeast strain.

It is about choosing a yeast strain and then manipulating its environment in such a way that you create your flavor profile. This will be amazing for whiskey. Less sour, less three-dimensional, more fruity flavors go form a warm fermentation only.

Now stay with me, thought experiment. What would you do if you were to make a vodka in this scenario? How would you ferment your beer in order to make a great vodka?

Vodka is relatively neutral, so you need less flavor. So what you basically do is you make sure that your pH is 5.2, 5.5, very close to neutral.

Common mistakes and decisions

We don't create those third-dimensional, earthy, rooty flavors. You make sure your temperature is under control. For sure not 30 degrees because at 30 degrees, most yeasts create a lot of fruity flavors which you don't want in a neutral product like vodka.

Now that's the way I want you to look at yeast and yeast management. It's about how you manage your fermentation in terms of temperature and in terms of pH. So we discussed how yeast has an influence on flavor.

Basically by your management of fermentation temperature and fermentation acidity. Does yeast as a strain or the package that you want to buy or maybe another variety that somebody advises you to purchase, does it have no influence at all? Because we started with distiller's yeast, right?

But what if we add baker's yeast instead? Baker's yeast is used to make bread. Bread goes into the oven where it still needs to do a little bit of work.

So baker's yeast is very resistant to high temperatures. So For example, we take another color and we plot on this chart baker's yeast. Baker's yeast is happy at higher temperatures.

That means that if we choose distiller's yeast or baker's yeast and we ferment both at around 30 degrees Celsius because we stress out relatively the distiller's yeast more, it will make more fruity flavors. For baker's yeast to actually create more fruity flavors, we need to stress it more. So we need to bring up the temperature of fermentation, maybe to 32 degrees, 33 degrees to get the same level of stress resulting in the same level of fruitification.

Another example, I'll take another color here, is about a customer that we had that had a brewery. So they made beer and now they wanted to make whiskey as well. And the beer they made and the beer they still make is a lager.

A lager, I'm not a beer guy, but I'll try to sort of summarize what I learned from it. A lager is a beer that ferments at a very low cellar-like temperature. So a lager yeast by definition is very temperature intolerant.

It doesn't like warm temperatures. So he made an amazing lager and then he used, he scooped off that yeast and he used that to also make his distiller's beer and then we tried to make vodka out of it. But because he was fermenting at 30 degrees, imagine the heat stress that this lager yeast that actually normally works at cellar temperatures like 10, 15 degrees Celsius instead of 25, 30, how much stressed out it was.

So the vodka and the whiskey that we were making or trying to make afterwards was too fruity.

Continue with This section mirrors the fermentation control model: pH and temperature steer flavor. to build directly on this foundation.

Key Takeaways