Definition of Ale or Lager yeast

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nilo

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We have heard over and over the statement "The difference between a lager and an Ale yeast is that a lager is a bottom fermentation and at cold temps and Ale yeast is a top fermenting at warmer temps".
Guess what, this is not what defines a lager or an ale yeast. I was told about this few yeast ago by someone that actually gratuated in brewing. He also shared few documents, which I paste below, so we get this cleared.

"LAGER VS. ALE
Strictly speaking, yeast that can metabolize melibiose (a simple sugar), are classified as Saccharomyces
Uvarum, or lager yeast, and brewing yeasts that lack this ability are classified as Saccharomyces
Cerevisiae, or ale yeast. In recent years the distinction between these yeast on a taxonomic level does
not correspond well with the actual performance of the yeast in brewery fermentations. A yeast may
have an ale yeast taxonomy (i.e. does not metabolize melibiose) but performs like a lager yeast in the
brewery (i.e. low temperature fermentation, bottom fermenting).
Top fermenters vs. bottom yeasts can be determined by cell wall composition. Can be tested by
placing in a clean test tube with H2O and shaking. Those that make a “skin” at the top are probably top
fermenters.

Saccharomyces Cerevisiae can ferment glucose, sucrose and maltose

S. Uvarum (Carlsbergensis) can ferment all including melibiose

S. Diastaticus can ferment all plus dextrins. Produces considerable quantities of diacetyl and is
considered a wild yeast."

That explain why a lager is drier and crispier than an ale, because a lager yeast can metabolize more sugars (Melibiose).

Anyway, just wanted to share this information.
 
Thank you, Nilo. I had heard the same information from various sources, but never took the time to confirm any of it since I'd never had to explain the different to anyone other than a brewer.
 
That explain why a lager is drier and crispier than an ale, because a lager yeast can metabolize more sugars (Melibiose).

I was with you until this part. Wort has negligible amounts of melibiose. Melibiose and raffinose fermentation are useful from a taxonomic POV but have nothing to do with performance in fermenting wort.
 
I was with you until this part. Wort has negligible amounts of melibiose. Melibiose and raffinose fermentation are useful from a taxonomic POV but have nothing to do with performance in fermenting wort.

I think I should have posted that last comment with a question mark at the end
 
Yeah, I heard about this a long while back, but it doesn't help the new brewers, or any of them really. Just an interesting note on how they are classified technically. I just pass on the bit about cooler ferments and bottom fermenting for lagers and that sets them on their way.
 
Ale vs lager? Can be a bit of a can of worms when you start to think about it too hard, even though we all know inside which is which :)

Not a can I'm about to open just now either...
 
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