From: jdg00@ccc.amdahl.com (Josh Grosse)
Newsgroups: rec.crafts.brewing
Subject: Re: Yeast comparisons
Date: 4 Oct 92 15:21:30 GMT
Reply-To: jdg00@amail.amdahl.com (Josh Grosse)
Organization: Amdahl Corporation

jworley@borris.eece.unm.edu (Jeremy Worley) writes:

>Has anyone compiled a comparison of dry and liquid yeasts that
>are available?  In particular, I am interested in general quality,
>contribution to overall flavor, "speed" of fermentation, esters,
>aromas, odors, etc. etc. 

Please see "Analysis and Evaluation of Commercial Brewer's Yeast" by Mary
Miranda, Setphen Ask, Jan-Xavier Guinard, and Michael Lewis, Ph.D., in the
1989 Special Issue of Zymurgy Magazine.  They compare 14 dry ale yeasts,
5 dry lager yeasts, and 3 liquid yeasts (2 lager, 1 ale).  They measure
them by Colony Forming Units per gram, percent fiability, fermentation rate,
doubling time, colony forming lactic acid bacteria presence, and enteric
bacteria or salmonella detection.

>Also, as a reletively new brewer (7 batches, all extract), I am 
>a little confused about the terminology used to describe yeast 
>flavor/behavior.  In particular, what exactly do the words 
>"attenuative", "estery", etc. mean?

Attenuation describes the types of sugars that can be metabolized by yeast.
Superattenuative can metabolize maltotetriose (4 glucose chain), attenuative
can metabolize maltotriose (3 glucose chain), and unattenuative can metabolize
only up to maltose (2 glucose chain).  Estery is a description of odor and
flavor constituents coming from esters (fatty acids combined with higher
molecular alcohols), typically fruity (raspberry, pear, banana, clove...).

>Some mail messages seem to indicate that attenuative yeasts are
>undesirable.  Why is that?

It depends entirely upon the style you are trying to achieve.  "Dry" beers use
genetically engineered yeasts which go beyond "superattenuative", for 
example.

>A description of other flavor "adjectives" would be useful.

There have been hundreds of flavors (some wanted, some NOT wanted) identified
in beer.  Here's a short list from the 1992 AHA/HWBTA judging sheet, which
judges can check off:

Acetaldehyde, Alcoholic, Astringent, Biter, Chlorophenolic, Cooked Vegetable/
Cabbage-like, Diacetyl/Buttery, DMS, Fruity/Estery, Hoppy, Husky/Grainy,
Light-Struck, Metallic, Oxidized/Stale, Phenolic, Salty, Solventlike, Sour/
Acidic, Sweet, Sulfurlike, Yeasty.

Each of these is explained on the sheet.

>While I'm at it, I have noticed that different brands of extract
>seem to have different different quantities of dextrins, resulting
>in variations from the expected final gravity.  (I'm sure that I 
>am stating the obvious, but bear with me , I'm a newbie)...has
>anyone compiled a comparison of extracts available.

The University of Saskatchewan did a study last year, in which gas
cromatography (I think) was used to make a spectographic analysis of
the contents of a number of malt extracts.  Their results were so
poor (some extracts actually contained NO malt) that they refused to
publish specific results by brand name.
-- 
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Josh Grosse                                jdg00@amail.amdahl.com
Amdahl Corp.                               313-358-4440
Southfield, Michigan