From the HBD Archive
From: Tony Burgess <BURGESS@vm.epas.utoronto.ca>
Subject: Twice-active yeast
Date: 1989-10-29 17:29:35 GMT

My most recent batch of beer has been doing some interesting things, and I wond
er if anyone can tell me what to expect from it.

The brew is made only from extract, horrible hops laden with orange dust, and a
liquid culture yeast called "high-temperature lager yeast", which claims to yi
eld best results when fermented between 10 and 16 degrees C. I use a two-stage
closed fermentation system, and in the first stage it performed admirably, tha
nks to our being able to maintain it at a fairly constant temperature of about
45 deg. F. After about a week, the kreusen was down, and we decided to rack --
and at about the same time the weather betrayed us and began fluctuating by as
much as thirty degrees daily. After racking, there was no sign of yeast activ
ity at all, and sg remained constant at 12 (having started somewhere in the low
fifties). This went on for about a week, after which the yeast came back to l
ife -- for the last five days or so there has been constant slow activity, thou
gh there seems to be no evidence of pressure in the vapor lock.

Noonan indicates that when yeast suffers temperature shock, a lot of it dies, a
nd the survivors mutate into new kinds of yeast which are by no means guarantee
d not to impart bad flavours to the beer; he also says that the autolyzed yeast
that results from such a wholesale slaughter will give the beer an indescribab
ly awful taste. In my experience, however, Noonan has a habit of over-emphasizi
ng how bad certain off-flavors can be, and so I'd like to know if anyone has ha
d this happen to their beer, and if so, whether the beer was a complete loss or
merely somewhat less wonderful than they had hoped.

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