hist-brewing: Medieval yeast culture maintenance

Hiram Berry burningb at burningbridges.com
Mon Mar 22 10:02:49 PST 1999

I have a couple of questions concerning medieval brewing technology that
have puzzled me for some time now, about which I hope those here have
some insight. First, how were yeast cultures maintained in
pre-industrial times?  They didn't have refrigeration, test tubes with
sterile culture media, or freeze drying in those days.  As I understand
it, brewing was essentially a kitchen task of larger households in that
period rather than an industrial operation, so year-round continuous
batch production doesn't seem plausible, and without ambient temperature
control summer and winter seasons aren't conducive to good results in
most locales.  How were viable yeast cultures preserved over several
months without introducing opportunistic bacterial infections while
using commonplace nonindustrial technology?

The other thing I've wondered about is the origin of ale yeast.  It
doesn't seem likely that it was found as a natural parasite of grain in
the manner of must on grapes-- the "malting" phase in nature is so short
that there wouldn't be enough time for the yeast organism to take
advantage of it.  Was it possibly a cidering yeast that someone adapted
for use on wort?  I understand that cider has a long history, still
maintained in some places like Cornwall, naturally propagated by wild
yeast on the fruit skin.  The possibility that someone tried using cider
yeast on malt wort doesn't seem implausible-- when some squeezed apple
juice I had started spontaneously fermenting, on a whim I tried using it
as starter for a batch of ale.  The result was quite palatable.  I guess
the only way to definitively decide this would be extensive DNA
comparison of different yeast strains.  Does anyone know if such work
has been done?

Just wondering,

Hiram Berry

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