Posted By on January 21, 2010

What’s the difference between top and bottom fermenting yeast?

I was just reviewing some older posts in my archive, seeing where corrections could be made, or erroneous information updated. I wanted to start with this one…

The Lager Debate in which I make the statement:

The main difference between yeasts used for lagers and ales is that ale yeast is a top-fermenting yeast which means the yeast floats to the top and hangs around up there during most of the fermentation process. Lager yeast is a bottom-fermenting yeast which means it hangs around the bottom of the fermenter. During both types of fermentation the active yeast does permeate the brew and eventually settles out on the bottom of the fermenter when it is done.

I was partially correct. During both fermentations the yeast is distributed throughout the wort while it is doing its thing. That’s where my accuracy ends. What’s wrong with that original article is my literal misinterpretation of the phrases “top fermenting” and “bottom fermenting.”

Top fermenting yeasts, ale yeasts, are called so not because they hang around at the top, but because they tend to generate a thick foamy layer along the top, contributing to krausen.

Conversely, bottom fermenting yeasts, most often used for lagers, do not contribute to a foam layer.

All yeast will mix in with the “solution” in order to consume sugars in the wort, or must in the case of wine making. All yeast will settle to the bottom of the fermentation vessel, creating a layer of silt, or sediment, when they’re through.

Well. That’s that. As I’ve mentioned in a previous post, I pride myself on presenting factual information here at Cryptobrewology, but learning is a process and my eagerness to share info may result in some inaccurate data sometimes. Never fear, I strive to self-correct, and urge you to contact me if you spot anything inaccurate on the site.

Happy brewing!

About The Author:

I've been homebrewing and learning about good craft beer since 1999. My wife, Cindy, and I enjoy road trips, exploring new places and finding great brewpubs and breweries. Explore with us through as we continue on our quest of Road Trips and BrewPubs!


2 Responses to “The Facts: Top & Bottom Fermenting Yeast”

  1. Well, you’ll want to make sure you use hops and malts are typically used for lagers. But basically, yeah, if you’re using a lager yeast and have designed your beer to be a lager, you need to ferment around 55 degrees, for a couple of weeks, then rack to secondary and lager it for another few weeks before bottling. Then, keeping the bottles at 40 degrees or so to let them settle out and crisp up. I rushed a lager just before Christmas. Fermented it outside so it was nice and cold (PA Winter) for two weeks, then I had to bottle it, so basically I skipped the secondary lagering step and just lagered in the bottle for three weeks, but it still turned out pretty good.

    Lagers take much longer than ales from fermentation to finished beer.

    Let me know how it turns out if you brew one!

  2. Aaron says:

    So, does this mean that the only difference I have to worry about when creating a lager at home is the temperature during fermentation?

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