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Cider Digest #1642
Subject: Cider Digest #1642, 8 July 2011
From: cider-request@talisman.com
Cider Digest #1642 8 July 2011
Cider and Perry Discussion Forum
Contents:
Cider apples/juice availability (Melissa)
Chemistry of SO2 (Andrew Lea)
Re: Pumps (Dick Dunn)
NOTE: Digest appears whenever there is enough material to send one.
Send ONLY articles for the digest to cider@talisman.com.
Use cider-request@talisman.com for subscribe/unsubscribe/admin requests.
Archives of the Digest are available at www.talisman.com/cider#Archives
Digest Janitor: Dick Dunn
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Subject: Cider apples/juice availability
From: Melissa <5happyapples@gmail.com>
Date: Thu, 7 Jul 2011 19:08:20 -0700
Hello,
I've been a lurker on this digest for years now and have so appreciated
the resource, thankyou to all that contribute. We farm 40 acres of
dessert varieties in the Okanagan Valley, Canada and are currently
pulling together a business plan for an artisanal cidery. I just
completed Peter Mitchell's excellent Mt. Vernon course and we are
planning to run 1000L of cider for market testing purposes this fall.
Dependent on those results, we will go forward with the plan next year
on a small scale.
I understand that the availability of true cider fruit (or juice) is
growing, however still difficult to come by, especially in Canada. We
have empty land that we will plant cider varieties on, but in the
meantime, I am looking for a small supply of cider fruit (or juice) for
pressing this fall - maybe around 500lbs. At this point, I am not picky
about variety as long as they are bittersweets/bittersharps - we have
plenty of dessert fruit for blending! If anyone can point me in the
right direction as to where fruit can be sourced from in Western Canada,
I would very much appreciate it.
A few more questions:
1) If anyone is familiar with the rules, I'd appreciate info on the
legalities of shipping fruit or juice across the US/Canada border, both
directions.
2) Recognizing we would base a business decision on further research
than this digest alone, is there sufficient demand for cider fruit/juice
that if we were to plant some of our bare land into cider varieties,
beyond our own requirements, that we'd be able to sell it? For what
price per pound do you estimate? Contingent as well on the legalities of
shipping cross-border of course, unless we could find enough demand here
in Canada.
3) Any tips that you can provide for a newbie like me about starting a
small-scale commercial cidery are always appreciated - here on the
digest or at 5happyapples@gmail.com :)
Thanks in advance,
Melissa
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Subject: Chemistry of SO2
From: Andrew Lea <andrew@harphill.co.uk>
Date: Fri, 08 Jul 2011 12:37:25 +0100
I'm afraid there was quite a lot of chemical misunderstanding about
sulphur dioxide apparent in the last Cider Digest. I'm going to try to
put that right.
First of all, the only effective form of sulphur dioxide as an
anti-microbial is the molecular or non-ionised form SO2. The ionic
bisulphite form HSO3- is not effective. The reason for that is that the
SO2 molecule has to cross cell membranes to get inside them and
interfere with cell function, and the ionic form cannot do that. The
level of molecular SO2 needed to kill or disable microbes varies
depending on the organism but for typical yeast inhibition is around 1
part per million (ppm). If you generate SO2 as a gas eg by burning
sulphur in air in a barrel you will get that molecular form which has
direct action as an anti-microbial.
For practical wine or cider making, there are three separate issues we
need to distinguish in more detail.
1. EQUILIBRIUM ISSUES. If you dissolve the sodium or potassium
metabisulphite salt in water, or dissolve SO2 gas in water, you get
predominantly the HSO3- (bisulphite) ion. This is not an antimicrobial
and can only be converted to molecular SO2 if the pH is low enough. The
equilibrium equation is H+ + HSO3- = H2O + SO2. The sum of both forms is
reckoned as 'SO2' but at a pH of 5 (roughly the natural pH of KMS
solutions) only 0.07% is in the molecular form. That's why it's
recommended to drop the pH in sulphite sanitising solutions, eg by
adding citric acid, to increase the proportion of molecular SO2. At pH
3, over 6% is in the active molecular form.
TAKE HOME MESSAGE 1. Distinguish between ionic (bisulphite) and
molecular SO2. Only the latter is an effective antimicrobial and its
existence in solution is determined by an equilibrium which depends on pH.
2. BINDING ISSUES. In real life juices, ciders and wines, much of the
added SO2 becomes bound to other molecules such as sugars and aldehydes.
The binding is also an equilibrium whose extent depends on the actual
binders which are present. In practice a 'rule of thumb' has to be used
since it would be impossible to determine accurately for every case. To
obtain 1 ppm of active molecular SO2 in a juice at pH 3.8, typically
around 200 ppm of total SO2 is required of which only 100 ppm is free
and only 1 ppm is active (round numbers). That is why pH 3.8 is taken as
the effectiveness cut-off to control wild yeast and bacteria since 200
ppm is the upper permitted limit of total SO2 in many jurisdictions.
TAKE HOME MESSAGE 2. Distinguish between bound and free SO2. Only the
free part can be useful and only the molecular part of that is actually
anti-microbial.
3. OXIDATION ISSUES. Under some circumstances it is possible for the
HSO3- bisulphite ion to become oxidised to SO4-- known as sulphate
(sulphuric acid). This is actually much more difficult than people think
and cannot easily be done by aerial oxygen. In cider and wines it
usually happens by 'coupled oxidation' mediated by polyphenols where the
active agent is hydrogen peroxide. Various enzymes or some metals such
as iron and copper can act as catalysts for this. This is how SO2 acts
as an antioxidant, by scavenging damaging peroxides, not by reacting
directly with oxygen. This step is not an equilibrium and cannot
normally be reversed. Sulphate (sulphuric acid) is not antimicrobial at
all in ciders and wines.
TAKE HOME MESSAGE 3. Irreversible oxidation of bisulphite to sulphate
can occur and is what generally happens when SO2 acts as an antioxidant.
GLOSSARY
TOTAL SO2 is the amount which you've added, all summed up (with the
exception of what small fraction might have been lost by oxidation)
BOUND SO2 is the proportion of the total which is currently bound up in
equilibrium with glucose, acetaldehyde, pyruvate and so forth.
FREE SO2 is how much of the total SO2 is not currently bound.
MOLECULAR SO2 is that part of the free SO2 which is available and
antimicrobially active in a molecular form as a result of the pH
equilibrium.
These relationships are shown in diagram form here
www.cider.org.uk/sulphite_distribution.png
Some further information is on my website at
http://www.cider.org.uk/sulphite.html and in particular there are links
there to the spreadsheets which show how all the equilibrium and binding
calculations are carried out.
I hope this helps. Sorry it's so complicated but I didn't invent the
chemistry and it isn't my fault!
Andrew Lea
nr Oxford UK
www.cider.org.uk
------------------------------
Subject: Re: Pumps
From: Dick Dunn <rcd@talisman.com>
Date: Fri, 8 Jul 2011 10:14:27 -0600
A few digests back, Nat West wrote:
> I bought a highly-recommended pump this year, the March 809, which I am very
> disappointed with. Apparently, it is a PUMP, not a SUCK. In addition to not
> being self-priming (if you have shut-off valves on each end of your tubing,
> it's not too much of a pain), it only pumps juice up, from the pump to a
> higher location. It does not suck juice into itself from a higher location.
(You meant "from a lower location" I assume.)
I would say that can't be right - except I had the same experience myself
with the March 809!
What I mean is that the pump can generate a fair head, which amounts to
pulling liquid in to push it up (substantial difference in pressure at
input and output sides). I've been able to start the pump at a lower
location, then lift it up while it's running.
I puzzled over the effect Nat describes for a while. I *think* it's that
(a) the pump won't pump at all if there is -any- air in the pump chamber,
and (b) it's nearly impossible to fill the pump chamber and keep it filled
(fully primed) when the pump is sitting above its inlet hose. Regardless
of the actual cause, the result is that the pump isn't useful unless it's
down low, and this turns out to be too much of a nuisance. I've given up
on the 809. This is also the reason I insisted in my earlier note that
a small pump, to be useful to a cidermaker, MUST be self-priming.
Oh...also, somebody had asked about the Euro-pump(s). Realize that these
require 230 V power, and are designed for 50 Hz. In the US, at 60 Hz,
they'd run faster hence not quite so gentle, but otherwise -ought- to be
OK. However, think about whether you can get 220-240 volt power where
you'll be working.
- --
Dick Dunn rcd@talisman.com Hygiene, Colorado USA
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End of Cider Digest #1642
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