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charter and species question

Daniel Zabetakis dan at cubmol.bio.columbia.edu
Wed Apr 28 17:28:47 EST 1993

In article <C6619y.8IG at news.cso.uiuc.edu> amead at s.psych.uiuc.edu (Alan D Mead) writes:
>I have just started brewing my own ale so it may be that I have a
>greater affinity for yeast than some of the more "academic" readers of
>this group. :)

   Just want to point out that there are some groups for home-brewing.
Personally, I don't mind this type of question here, since I'd like to 
learn more about the practical uses of yeast. I just want to make sure that
you know that there may be better groups to go to.

>So I hope this is an appropriate place to post my yeast questions.  If
>there are basically two species of beer yeast, why are there so many
>strains sold?  I thought that the species was the finest categorization

   Not by a long shot. Personally, I'm not even sure how you distinguish
species in yeast. Strains can be very different. Evenn if they are not
extremely different, they will have subtle differences in thier biochemistry.
  I guess a yeast strain is sort of like a human race. While two strains
may be of the same species, they are different enough to be separate, and
among themselves close enough to be grouped.

>Also, just out of curiousity, brewers are cautioned to be fairly
>careful about sterilization to prevent wild yeasts and other uglies
>from turning the batch bad.  But at the same time, wine and beer have
>been brewed for centuries (millenia, actually).  Did infection used to
>be common or are we home brewers just overly paranoid? 

   Probably both. You certainly wouldn't want to culture any human pathogens,
and the conditions for yeast growth are often very similar to those for
bacterial growth. Better to be safe than sorry.
   It is my impression that in past times, mild food poisoning was an
almost daily occurance.

> What procedures
>are common in laboratories to keep cultures pure?

   Ha. If you could patent a way to keep cultures pure, you'd make a
fortune from us yeasters. 
   About the only thing we can do is keep our strains in frozen stocks at
-70 C. Also, after a while, your culture will start behaving differently
if you continually subculture it. We always go back to the frozen stock.


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