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Cider Digest #1521
Subject: Cider Digest #1521, 28 July 2009
From: cider-request@talisman.com
Cider Digest #1521 28 July 2009
Cider and Perry Discussion Forum
Contents:
Is it too late for copper? (Andrew Lea)
Yeast musings (Andrew Lea)
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Subject: Is it too late for copper?
From: Andrew Lea <andrew@HarpHill.co.uk>
Date: Sat, 25 Jul 2009 21:48:01 +0100
Jason wrote:
>
> I recently sampled an unbottled 30 gallon barrel of cider from last
> years pressing. It has, I hate to say, a cooked cabbage flavor
> which, I venture to guess, is not what most people want when they
> open a bottle of cider.
> I am curious about trying to clean this up with a little copper, but
> am not sure if it is too late. I have heard that copper is more
> effective against the "rotten egg" smell than the "cabbagy" smell,
> although I believe that both are produced by the same compounds at
> different points in their life cycles.
I don't know if it's too late or not but there are a number of things
you can try. Received wisdom has it that hydrogen sulfide goes to methyl
or ethyl mercaptan both of which are removable with copper. Next step is
the formation of diethyl / dimethyl disulfides which are not. However
they can be reduced back by treatment with ascorbic acid, and then
removed with copper. The mercaptans and disulfides are more cabbagey
than H2S.
Zoecklein's Wine Analysis book gives the following procedure for
*testing*. You need stock solutions of cupric sulfate in water (1%) and
ascorbic acid (10%) in water.
Fill 3 wine glasses with 50 ml of cider. One is the control. To the
second add 1 ml of the copper solution and mix. To the third add 0.5 ml
of the ascorbic acid solution and stand for several minutes. Then add 1
ml of the copper solution and mix. Evaluate the aromas (do not taste by
mouth!).
If glass 2 is best, then all you need is the copper. If glass 3 is best
then you need ascorbate too.
Now, for *treatment*, you need much more dilute solutions. General
advice is no more than 1 ppm copper (as copper). That's a maximum
addition of 400 mg of cupric sulfate per 100 litres (30 US gallons is
around 113 litres). I would start at around the 100 mg mark and step up
as required. You've already got your 1% stock solution which is 1000mg
per 100ml so you should add just 10 ml of that to the cider in the first
instance. I would wait an hour or so before deciding whether you need to
go up to a higher level.
If you already know from the testing that ascorbic acid is required then
add about 50 ppm (50 mg per litre or 5 grams per 30 gallons) and let it
stand for maybe 15 - 30 minutes before the copper addition. That's a one
time addition even if you decide to increase the copper.
I have personal experience of making the straight copper addition work
but never the ascorbic step - good luck if you need to do it!
Oh and do check my math - I think i got it right but it's always worth a
double check to be sure!
Andrew Lea
nr Oxford, UK
www.cider.org.uk
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Subject: Yeast musings
From: Andrew Lea <andrew@HarpHill.co.uk>
Date: Sat, 25 Jul 2009 22:09:21 +0100
I have a couple of yeast musings for the 'silly season'. They're so
obscure I've wrapped them up in the one post!
1. Most fermenting yeasts (wild or cultured) are generally regarded as
'glucophilic' so that they preferentially metabolise glucose before
fructose. Apple juice is about 70% fructose, 30% glucose. What effect if
any does this have on the fermentation rate or final gravity of a cider?
Has anyone ever seen any data on loss of individual sugars in
cidermaking? Do F&G both go at the same rate or does all the glucose go
first? If so, does the rate of fermentation slow down at that point?
2. I've heard tell (or maybe I dreamed it?) of cidermakers who make
(naturally sweet) bottle conditioned cider who measure the yeast cell
count at bottling to be sure it won't become a 'bottle bomb'. This needs
the use of a (hemo)cytometer slide and a reasonable microscope as far as
I can see. Does anyone know if this is ever done? If so, what's their
yeast number cut-off point? And, if anyone does this, do they make any
attempt to measure the YAN (yeast assimilable nitrogen) at the same time
too?
Maybe someone out there who's a winemaker turned cidermaker has some
answers?
Enjoy the summer (for those of you in the Northern Hemisphere, that is!).
Andrew Lea
nr Oxford, UK
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End of Cider Digest #1521
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