On Mon, 14 Jul 2003, Bill Bell wrote:
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> Greetings,
> I've often cloned yeast from bottles of beer I've enjoyed (both homebrew and
> commercial), with good results. But I've heard that if you clone the same
> yeast too many times, mutations result that affect the flavor of the beer.
> A few questions come to mind:
> * Is this true?[/color]
If by "clone" you mean that you isolate yeast from a beer, then
mutations can and do occur. However, you should start with a few cells
from the beer and always select many cells when you restreak the yeast
onto new media. This way, if there is a mutation in a single yeast, you
will be including plenty of other yeast thta aren't likely to have the
same mutation.
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> * On average, how many times might I expect to be able to clone a yeast
> colony before it is significantly different from the original strain?[/color]
Depending on the conditions you keepm them under, you could keep yeast
that would give the same flavor profile long enough to give to your great
grandkids. (Probably could keep them indefinately)
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> * What is the nature of the mutations? i.e., What sort of flavor changes or
> other behavior might I expect? Don't wanna brew no skunky beer :)[/color]
Mutations are random, but if you don't select a single colony to
make your starter with, the contribution of those mutation likely won't be
noticed.
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> * How do the yeast labs (Wyeast, White Labs, etc.) perpetuate their yeast
> strains without the same thing happening to them?[/color]
Cryogenics. They freeze their yeast to stop biological activity,
i.e. mutatuions.
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> * Finally: Maybe mutations aren't always a bad thing. Has any of our group
> deliberately mutated a yeast strain so as to "encourage" mutation in a
> certain direction?[/color]
Haven't done it yet because there are so many yeast available one
doesn't need to create his own special yeast strain.
Warren Place