Posted By Drew Vics 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.