Backset Cycle Explained: Build Flavor Across Runs

Apply a practical sour-mash style loop: replace part of mash water with hot backset, monitor pH limits, and run enough cycles to reach repeatable high-intensity output.

Quick summary

Core principle

Okay, the grand finale of the iStill Distilling University Online and there will be topics after this and we'll go left and right and you'll bring up topics, but this is my favorite part. This is like, okay, so we challenged you, right?

This is how we want you to use various toolboxes to mash correctly, to ferment the way that suits your spirit style, to distill the way that suits your spirit style and have all kinds of tools to actually go left or right, go more intense or go lighter on flavor. So you're ahead of the game now.

Now, you may think like, I'm just starting out. I've got the meaning, I've got the course, amazing information.

Let's talk to a master distiller from around the road, a guy that works at a large corporation making big alcohol. Why this part, virtuous cycles as it's called, is going to be even more fun is because we're going to take everything taught you so far to a new level.

Virtuous cycles, there's something like vicious cycles, like significant goes down the drain and it just spins out of control and it gets worse and virtuous cycles intend to mean that things get better in a cyclic way. So I want to train you in cyclic thinking.

Distilling is a process with a start and an end. For grains, for example whiskey, you mash to create fermentable sugars.

You ferment to create alcohol and flavors. You strip, let's stay with the traditional approach for a moment.

You strip to create low wines, an intermediary product, and you finish to create new mixed spirit that you then age, bottle, et cetera, and then you start all over again and that's not the way it works. With all the tools we've given you so far, you are able to bring your quality up to a level probably not seen before in your region, but how can we make sure it's not just that very high level but that it's so high that it sort of reaches the ceiling of what you can reach in terms of flavor profile and flavor intensity.

For that, I need you to think outside of the box with me and start to think cyclically. And let's do that with a few different colors.

There's basically three cycles I want to go through with you. What do we do during fermentation?

Most people say, we create the alcohol. And if you've listened carefully to what I had to share, what we had to share the last few weeks, but for you it's probably the last few days seeing all our videos, one after another hopefully, because you enjoy watching them, flavor, 80% of flavor and alcohol.

But in most of these processes, that is not all we make. We make something else, maybe a rest product.

Let's start with a stripping run or if we do a one distillation or a 1.5 distillation approach the first run or maybe the last run in that process where there's organics present. Because at the end of the stripping run, we created something else, something that is left in the boiler, very often called stillage, boiler residual.

How it works in practice

You got your low wines out, the alcohols are out and hopefully the best flavors and you're left with a boiler, maybe in a 500 liter still, 300, 350 liters of a water grain mixture. Water grain mixture that has been boiled for six, seven, eight hours. The term I like to use for this is back set.

So we're left with a boiler almost full of back set. They'll go to the finishing run. But we created something else.

If we look at what we created, we can say a few things about the back set. First of all, is it cold or warm? Well, it's hot like water boils at 100 degrees.

The end of the run, end of the stripping run, you're very close to 100 degrees in there. So there's a lot of energy in there. We boiled on the grain, right?

You followed my advice, hopefully. For example, we're making whiskey and what's there? All the sugars were converted, right?

All the sugars were converted to alcohol. So is it sweet or sour what's left inside your boiler? Does that sound like something we could use?

Do you remember the esterification formula? Alcohol plus organics in a sour environment, hot, time, liquid, et cetera. So what if we use that back set for our next mash?

You start mashing by adding grains to warm water. The grains have the flavor, right? What if we have 500 liter, 400 liter of mash water and 100 liter of grain to make a 500 liter batch?

We make low wines during the stripping run. And we've got boiler leftovers that we call back set. And that back set is both energy dense, nutrient rich, and low in pH.

What if we take the water from that, the grains we don't need, the spent grains we can get rid of, but the watery bits and replace part of the mash water with back set? What if instead of using 400 liters of water for the next, for the second mash, we just use 300 liters of water and maybe 100 liters of back set? What would happen if we think circular instead of linear?

We create more flavor because water, 400 liters of water, didn't have any flavor. But 300 liters of water, 100 liters of back set, and 100 liters of grain have more flavor because your back set is flavorful. It also sours up your fermentation.

What happens to a more sour fermentation? And more back end flavors, more tails associated, rooty, nutty, earthy flavors. What happens to the fermentation once we strip?

What happens to the strippings, the low wines that we create during the next, the second run, the second run that we do this now with some back set? We create low wines with more flavor because we use less water and we ferment at a more sour environment. We don't need to pitch yeast nutrients because this is boiled grain and yeast.

It's all present in the back set so we can save some money there. And what happens if we do it a third time? Because we created more flavor strippings, we also created more flavorful back set.

So the third time, we get even more flavor. And the fourth time, we basically hit that ceiling that I spoke about. Three to four cycles and you're at your maximum of flavor.

So use the back set cycle for three dimensional products like medium to heavy or heavy rum or whiskey, right? Because pH means back end flavors, lots of flavors, lots of three dimensionality with a focus on the third dimension, back of mouth. You save energy, lower pH, you don't need to add nutrients.

The model grows like this into this direction.

Common mistakes and decisions

After three cycles, you reach your maximum. You can just continue, continue, continue. Very consistent and a lot of flavors.

Especially this cycle, the back set cycle, a lot of back end flavors. So ideally for rum and especially for whiskey. Now, this procedure isn't invented by me.

I did have to sort of redesign it. It is known in the whiskey world as sour mashing. They use stillage or back set to sour up the mashing process.

Sour mash in America, you need to use 25% or replace 25% of your mash water with back set to be able to call your whiskey a sour mash whiskey. For me, I want you to play around with the flavor profile you're happy with. I've gone to 50% sometimes, but you do run into issues with your pH.

So your fermentations tend to get stuck. Or you get an issue that if you don't use enough, that you don't get enough flavor. I love working with the back set cycle.

But we have to realize that with a back set cycle, there are limitations on how much you can use, especially since you're souring up too much for the yeast to still work. You have to stay above four, I would say. This discussion is related to a very important discussion, again, surrounding whiskey, which is called water.

Our whiskey is amazing because we have amazing water. And then you go to one of those whiskey shelves and you see somebody walking around with water from wherever, a very special place. And then they have some whiskey and they add some water because water is important.

That is not really what's meant there. What's meant with water being tremendously important for whiskey is that water from certain areas has more calcium than other areas. Low country, low flat water basically runs through turf.

It's very low in calcium count. Mountainous water falls down rocks, picks up a lot of calcium on the way, and it's very calcium-rich. Calcium-rich water, calcium is a buffer against pH drops.

So calcium-rich water, if you make whiskey in a calcium-rich water environment, doesn't go down in pH that quickly, because the lower it goes, the more calcium dissolves and the calcium brings the pH back up. So if you've got calcium-rich water, you can add more backset, maybe 40%. If you are in lowlands water, you basically are dealt a worse hand because maybe you can only add 10% or 15% of backset before your pH starts to crash.

That's something you don't want to do. And this is basically also the explanation why Highland whiskey from Scotland is considered to be superior to lowlands. It's not because they have a better feel for it or because their water is better and they talk about bottling water.

It's about the water that they make their fermentation and their mashes with.

Continue with Connects backset acidity to pH-driven flavor control. to build directly on this foundation.

What Backset Contributes

Backset carries acidity and late-run character that can accumulate cycle-to-cycle. Used with limits and pH control, it can deepen profile and stabilize house style.

Key Takeaways