From the HBD Archive
From: Conn Copas <>
Subject: Removing blow-off
Date: 1992-04-23 15:05:26 GMT

> - Bryan
>BTW, should I be skimming the foam out of the bucket? Or was
>this the topic with no consensus?
People may remember that I proposed an experiment on this issue a while back.
The basic idea was to take some blow-off, dehydrate it, then add it back to an
acidified water/ethanol solution and note any effects on colour, taste, etc. I
did something like this by taking the blow-off from a 5 gall stout brew and
adding it back to 1 gall of acidified water. OK, I didn't check ethanol
solubility, but I did concentrate the solution by a factor of 5 times what
would normally be encountered. The second thing I did was to take the 1/2 gall
trub remaining after racking into the primary, and give it the same treatment.

As we all know, both blow-off and trub taste foul. The dehydrated trub, in
particular, was so intensely bitter that not even 1 litre of homebrew, applied
orally, could alleviate the situation :-). The two substances appeared to be
chemically different, as the blow-off dissolved with considerable effervesence,
whilst the trub did not. Actually, the blow-off didn't dissolve, because it
preferred to sit on the bottom, despite all my best stirring efforts. After two
weeks, it had had negligible impact on colour or taste. Conclusion - removing
the blow-off is of questionable utility, unless you subscribe to the view that
the yeast may metabolise it into fusel oil during its anaerobic phase, which is
doubtful as far as I understand it.

The dried trub contained considerable sugar and gave a rehydrated gravity of 6,
with an opaque black colour. The solution tasted pleasantly bitter, which led
me to wonder how much hop utilisation is lost by precipitation. On the strength
of these observations, I decided to add a pound of sugar, some yeast, and
ferment away. I deliberately gave the brew no nutrient and pre-boiled it to
drive off any oxygen. Thus, in theory, I should be making a headache-inducing
brew of fusel oil. At the moment, it is fermenting powerfully and tastes/smells
quite pleasant. I'll keep the list posted on further results, provided I
survive :-)

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