What Does Autolysis Mean and How Can It Affect Beer?

For brewers, autolysis can be a mixed bag. It can be delightful, or it can be really, really bad. So the questions we have to ask are, what does autolysis mean actually? How does it happen? How does it affect beer? And what, if anything, can we do anything about it?

Autolysis

Autolysis is literally defined as self destruction. In fermentation, autolysis happens when yeast gets so stressed out that it self destructs, it basically internally combusts, with the insides of the yeast cells bursting forth and spewing itself throughout the fermenting beverage.

This process can be a delight in wine as it adds what is referred to as “yeast bite,” which is described as meaty. It adds a richness, a fullness if you will, to wine, so much so that autolysis is sought after in wine and especially in champagne.

It can also be described as sulphuric, bitter, and sharp as a result of the amino acids released by the yeast cells. These aspects are not only sought after in wine. This aspect of autolysed yeast is also highly sought after in many food products like barbecue potato chips for that same meaty bite.

Another consequence of yeast autolysis is enzymatic digestion, in which the yeast cell leaks proteases into the beer. The proteases digest the proteins in beer, which then affects the head retention, leaving beer with a foam that quickly goes flat. Enzymatic digestion can also cause those proteases to digest the complex sugars in bottle conditioned beers, converting them to simpler sugars. The simpler sugars can then restart fermentation, causing bottles to explode from excess carbonation.

Beer

Autolysis really only seems to be a problem, when it is a problem, in beer. In wine, vintners actually aim for autolysis, intentionally stressing yeast to encourage the reaction that will flesh wine out during aging.

And the truth is, autolysis is not all bad, even in beer.

During the aging process, in moderation, autolysis can actually highlight wanted flavors in beer and introduce more body for enhanced texture.

It all has to do with how fermentation is handled.

Fermentation and Yeast

During fermentation, yeast can be handled and mishandled in many ways.

The reality is that yeast is not meant to die off completely during fermentation, a common misconception.

The ideal fermentation process not only allows for yeast to survive but also to thrive.

Yeast really only has one job, the same it has had for millions of years.

This single celled eukaryotic living organism has thrived on earth in search of fermentable sugars like fructose and glucose for its entire existence.

Consuming sugar gives yeast the energy to procreate as it does asexually, creating a daughter cell that grows from its original mother cell. The daughter cell then detaches from the mother once it has reached 50% volume of the mother and begins its own search for sugar.

Alcohol and carbon dioxide are the waste products that come from that digestion of sugar, and that’s how we get our fermented beverages.

Now, in the traditional recipe, grain is grown by the farmer and purchased by the brewer. The brewer roasts the grain to the desired darkness and grinds the grain. These two steps convert the carbohydrates into sugar, which makes for better fermentation, and expose those sugars to the water it will be added to, creating a sweet “wort.”

The grain would then be added to water and boiled, and mashed in, or allowed to steep. Then, historically, wild yeast in the local environment would be naturally attracted to the sugars in the wort.

If and when autolysis did occur, it would be in small amounts as older or weaker yeast cells died off. Some self destructing cells would release those proteases, but others would be consumed by other, younger, stronger yeast cells for nutrition.

When left to the most natural process possible, yeast does quite a good job of cleaning up after itself.

Even if you have a bit of excess autolysis causing off flavors, new, fresh yeast added for secondary fermentation after racking can clean it up.

But sometimes it’s not that simple.

What to Do About Autolysis

Sometimes autolysis is out of control and you end up with a truly bad batch that is not only undrinkable but also downright unapproachable.

In this case, the beer must be tossed, and the brewer needs to check that proper handling procedures are undertaken.

Really, it is all about prevention.

Older yeast tends to be more easily stressed, so be sure to keep your yeast vital and viable, regularly checking the status of both.

Yeast that has been repitched multiply times can start to wear out and age, so use your yeast cell microscope after each new cultivation and harvest to check your yeast cell viability. Pitching too many dead yeast cells comes with a higher risk of yeast autolysis.

And be sure whatever yeast you used matches the alcohol content you are aiming for, as a yeast exposed to too many fermentable sugars and that has a low alcohol tolerance will quickly become overwhelmed by its own production and, you guessed it, get stressed out and self destruct.

Each of these measures taken will help you avoid a destroyed batch of beer, and as you try one step and then another, you will master your craft and become the resident expert on ideal autolysis in beer.

What could be better than that?

Cheers!

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