Yeast Starters: Getting Your Beer off to a Great Start
It may seem like a lot of extra time and effort to make a yeast starter. After all, people just pitch yeast straight from the tube or smack pack every day, right? Don't their beers turn out fine?
Well...yes and no. You certainly don't have to make a starter just to have a successful brew, but getting your yeast started ahead of time is actually a pretty simple way to reap a lot of great benefits. In this article, we'll take a look at the benefits of making a starter, take you through the steps of how to do it right, and then share a lot of practical tips from our team and the AIH community.
How A Yeast Starter Benefits Your Beer
Using a yeast starter can immediately improve the results of your brewing process in a few ways. Let's take a quick look at those benefits, and then we'll get more into the details of "why".
- Accelerated Fermentation: Your active fermentation is going to get underway within the first few hours after you pitch it, rather than 24-36 hours later. Not only does that cut down on the overall time for your primary, but it also means that you're much less likely to end up with a fermentation that gets "stuck" at some point along the way.
- Lower Risk of Infection: Because you're creating a sterile environment much more quickly, cutting down on the chances of ending up with haziness, off-flavors or — worse yet — just a spoiled batch.
- Better Attenuation: You're much more likely to get to a lower final gravity when you use a starter, compared to pitching without one. If your FG is consistently a little high, one of the first things you should try is switching to making a starter.
- Clearer Beer: One of the things that we often hear, after a customer makes their first starter, is "The beer was so clear!!" As you might guess, "better attenuation" = "clearer beer", but there are actually several reasons that a starter can lead to a clearer final product.
How a Yeast Starter Works
To understand why a yeast starter can bring you all these benefits, it helps to understand the cycle that yeast goes through once you pitch it...and how that cycle is affected when you make a starter:
Lag Phase: Waking with a Jump Start (AEROBIC)
Dormant yeast cells carry internal stores of a carbohydrate called glycogen. When the dormant yeast are exposed to the oxygen and nitrogen in your wort, they quickly start metabolizing that stored glycogen into glucose. That jolt of energy they produce in this "Lag" phase jump-starts their cellular metabolism, and allows them to begin reproduction. This is when your wort is actually most susceptible to contamination, since it is not yet an environment that is hostile to unwanted bacteria. A slight infection that takes place at this point won't necessarily ruin your beer, but even when you can't taste them, low levels of infection are actually a common cause of cloudiness and hazing.
Growth Phase: Explosive Reproduction (AEROBIC)
In this stage, the yeast continue to consume oxygen and nitrogen from the wort, and use it to fuel a huge rate of reproduction — the population of yeast cells will often double or triple in the first 24-48 hours. One of the unavoidable by-products generated during this aerobic process is diacetyl, which can give your beer a butterscotch-y flavor — you usually want to avoid it. The yeast will actually start re-metabolizing and removing diacetyl later, during fermentation.
Fermentation Phase (ANAEROBIC)
Fermentation only begins in earnest once most of the available oxygen has been consumed. (Past this point, any oxygen in the wort starts to mainly fuel chemical processes that we don't want, so limiting the introduction of any new oxygen becomes very important.)
As we all know, the yeast are now transforming the sugars in your wort into alcohol. That's not all that they're doing, however. There are a number of secondary processes that are also going on, such as the re-metabolization of any diacetyl, and the conversion of other, more complex starches. There's an important wrinkle, however -- yeast cells get the most energy from converting sugars, and so those other processes are suppressed while they have sugars that are freely available.
Sedimentation Phase (ANAEROBIC)
In the final stage of "sedimentation", the yeast respond to the fact that they are locked in a contained system, and begin to clump and go dormant. Their closed environment is growing increasingly more hostile — with a dwindling food supply and growing levels of toxic alcohol — and the yeast begin to generate a sticky protein that binds them other cells when they collide. This clumping process is called "flocculation", and it is essential to the brewing process.
Flocculating High and Low
Each strain of yeast has its own specific tendency to clump and fall out:
- High-Flocculating: "High-flocculating" strains, like British Ale yeasts, very readily clump and fall out of fermentation when they run out of resources, which makes them especially useful for brewing ales. The dormant yeast that collects on the bottom of the container is conveniently separated from the active yeast on top, and since ales usually don't go through the same extended, cold storage that lagers do, a high-flocculating yeast helps with the final clarity.
- Low-Flocculating: "Low-flocculating" strains do not precipitate as quickly once primary fermentation has completed, and can potentially stay suspended until you serve them. For some beers, especially wheat beers such as Hefeweizen, this is actually desirable, since the yeast contributes to the characteristic flavor, aroma and characteristic cloudiness of the style.