From the HBD Archive
From: sco!arthure@ucscc.UCSC.EDU
Subject: unknown
Date: 1989-02-04 00:21:05 GMT

> Date: Mon, 30 Jan 89 15:00:08 EST
> From: (Jay Hersh)
> Subject: blowoff
> Mike Fertsch was wondering why big brewers don't use blowoff. I think he
> or someone else indicated that at least one of them does. I was pondering
> this question with the people at catamount a few months ago they didn't know
> eihter but I think I have now realized the answer.

Many commercial brewers ferment in open containers.
Since the environment of the brewery can be controlled
more easily than that of the kitchen cabinet or closet
in which homebrewers may ferment their beer, they can
use open fermentation vessels, meaning they can skim
the scum off the top.

> What do homebrewers typically do that commercial brewers typically don't.
> Aerate the wort!
> When wort is aerated there is lots of free oxygen in solution in it.
> For those of you who have been studying yeast metabolism, something I
> have been looking into a lot lately.
> Aerobic fermentation, where free oxygen is utilized, occurs via a
> different chemical reduction process than anaerobic fermentation.
> It yields far more energy than anaerobic fermentation does, allowing
> the yeast to reporduce more rapidly. Since it uses a different reduction
> mechanism it produces different fermentation by-products, many of these
> the "higher alcohols" like fusel alcohol.

I don't know about not aerating the wort; the local
brew pub seems to do so, and I'd been lead to believe
it was important to the growth of the yeast.

As far as the gunk goes, Charlie Papazian talks about
"fusel oils" and hop resins and seems to believe that
the undesireable elements are from the hops, not from
fermentation. He may be mistaken about some of these
ideas, but it seems unlikely he would call something
an oil if it were an alcohol.

not a biologist,

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