From the HBD Archive
From: Dave Sheehy <dbs@hprnd>
Subject: Oxidation, Gelatin, et al.
Date: 1989-10-25 17:56:15 GMT


>>From: Martin A. Lodahl <pbmoss!mal@hplabs.HP.COM>
>>Subject: Trub Management
>> eight-year-old asked, "why don't you just use
>> your lauter tun?" My jaw dropped. Since the
>> wort is already cool, oxidation is not a problem.
>The reason that oxidation is not a problem is not because the
>wort is cool, rather because before yeast goes into its fermentation
>stage of life, it goes through a respiration stage during which it
>NEEDS oxygen. Boiling drives off oxygen (and all other dissolved
>gasses, for that matter) so that you need to aerate your wort before
>pitching your yeast. After fermentation begins, you then need to
>be careful to not introduce oxygen.

Whoa! Wait a minute here. According to Miller oxidation is a problem with
hot wort. Yes, you want to oxygenate the wort before it's pitched but only
after it's been cooled so that oxidation is not a problem. In fact, that's
one of the reason's for using a wort chiller (as well as getting a good cold
break). If the wort is allowed to cool slowly then it will subject to more
oxidation according to Miller.

I suspect that's an unstated reason for doing partial boils when extract
brewing. Adding cool water to the boiling wort to bring it up to volume
also lowers the temperature of the wort enough to limit oxidation. I
unwittingly experimented with this when I did a full boil of an extract
recipe that I've made many times before. I don't have a wort chiller but I
did place the fermenter in a bath of cool water. Still, it took several hours
to cool down. The resulting beer was ok but the flavor just wasn't as good
as it has been in the past. According to Miller, it should have turned out
better. The only difference between the two batches is that the partial boil
was added to cool water in the fermenter. Has anybody else had this kind of
experience? If you've had any experiences with oxidation how much did they
affect the flavor of the beer? My experience is that it's a second order
effect. The flavor is definitely affected but not in a major way (i.e. the
beer was undrinkable).

While we're on the subject of oxidation, I'd like to discuss Miller's
contention that the typical 1 - 2" headspace in a bottle of beer has enough
oxygen present to cause significant oxidation. Miller recommends using a 1/8"
headspace to prevent this. I'm not sure I believe him or not. I remember
some discussion a few months ago about headspace. Has anybody experimented
with a smaller headspace and if so did you notice any differences one way
or the other?

Gelatin and extended fermentation

>I have a question posed by a fellow homebrewer who doesn't have
>access. He had a batch that brewed in the cellar for some time (I
>can't remember how long) when he thought fermentation had slowed enough
>he brought it upstairs and put some jelatin (sp?, to clear it up) in
>it. After he did that it continued bubling for the next few weeks and
>he's wondering if the yeast could be acting on the jelatin or if it
>might be dangerous to drink the beer now. Any info?

You know, I've had this happen to me just about every single time I've
brewed. I've waited until there has been no activity in the primary whatsoever
but sure enough, when I rack to the secondary and add gelatin I start getting
fresh activity a few days later. I don't think the gelatin has anything to
do with this rather the mere act of agitating the wort rekindles the yeast
into activity. I've gotten into the habit of turning my fermentor around in
a circle to stir up the settled yeast and this seems to produce fresh activity
but I still get additional activity in the secondary. The beer has always
turned out so I don't worry about it anymore, I just deal with it.

Wort Foaming During Bottling

The last batch of beer I bottled foamed (or fizzed if you will) while I was
bottling it. It did this so much that I had trouble maintaining the sipon
in my transfer tubing. If I stopped for any amount of time a big bubble
would form in the tubing and I'd have to purge it. Anybody have any theories
why this happened. I swear it had fermented out, it fermented normally in the
primary for about a week and sat in the secondary for another week, week and
a half. In the secondary, it showed little activity. Boy, but when I bottled
it it foamed like mad. After several weeks of bottle conditioning it tastes
fine. It forms a large head but it's very coarse and doesn't last long. Any
clues as to what's happening.

Wort Chilling

I just tried chilling a batch by immersing a 1 gallon milk jug filled with
water and frozen solid into the boiler. Boy, what a difference. It really
enhanced the effect of the finishing hops. By cooling down the wort immediately
the aroma and flavor of the finishing hops were retained more than before. An
immersion chiller is going on my wish list.

Dave Sheehy

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