From: Tom A Brown <EUSTOBR@am1.ericsson.se> wrote:
>Bread yeast & brewer's yeast are different, apparently not
>interchangible.{due to flavor?] I am interested in the differences
>in how yeast(s) behave. How can such a simple mold be so
>smart??
>Home brew beer and soda both use (the same) brewer's yeast.
>Why not bakers yeast? And why not bake bread with Brewers
>yeast?....
The following from Byron Burch's excellent book "Brewing Quality
Beers" might help explain: "It is true that beer yeast and baker's
yeast descend from the same ancestral strain, S. Cerevisiae, and
that both baker's yeast and ale yeast are still officially designated
by the same term, but this is misleading. By means of mutation and
selection over millions of yeast generations, the two industries have
evolved yeasts vastly different in character. Beer yeast, for example,
can be used in making bread, but it would probably take up to five
or six times as long for the bread to raise. By the same token,
baker's yeast tends to ferment at an erratic pace, often lends a
strong, yeasty flavor to the beer. It settles out poorly, and that
which does settle is easily disturbed when the beer is poured."
All humans belong to the same species: homo sapien. However
no one would question that some of us are better genetically
predestined to do some things better than others. The child of
two large, athletically built parents is likely going to have a better
chance at athletic success in football than the child of two frail,
thin and short parents. The fact that we all belong to the same
species doesn't mean either we or all yeast are exactly the same.
And, unlike the human population which intermixes quite freely,
both brewers and bakers go to great lengths to keep their
strains of yeasts quite pure.
>But such is (obviously) not the case with soda. Why is there no
>alcohol produced in the homebrew soda process, and what stops
>the yeast?
Actually, alcohol is produced in homemade root-beer and other
sodas, usually resulting in an alcohol content of about .25% to
.5%. Traditional home made root beer is only allowed to fermet
for a day or two, and then is moved to refrigeration. If a temperature
senstive yeast is used, this should reduce the continued fermentation
activity. The refrigeration (or intentional settling and removal of the
yeast) should stop most fermentation, but there is always the
danger of continued fermentation and the eventual explosion of
the root beer container. The web site:
http://hbd.org/brewery/library/RootB.html
has a nice overview of this process.
- Mitch