Amount of metabisulphite to add...

[winters...@gmail.com]

I would very much appreciate confirmation of my calculations on this, as its my first time with this sort of volume of cider.  I am well after fermentation about to store/age 220 gallons of cider in a SS tank.  I want to dose with sulphites at a 50 ppm level.  I believe I then need to add 110 grams of sodium or potassium metabisulphite to about 37 ounces of water and add that mixture to the cider.  Does that look right?  I assume I need to dissolve it in the water first, for if I just put the metabisulphite directly into the cider it might not dissolve well, correct?  Many thanks.

[Kyle Bryant]

First off sodium metabisulphite and potassium metabisulphite have different amounts of available SO2. Sodium metabisulphite 64% available. Potassium metabisulphite 55% available. Equation I use.

Amount to use(g)=[SO2 req.(mg/l) x #of Liters]/1000 x (100/64)-----this is for sodium metabisulphite
Amount to use(g)=[SO2 req.(mg/l) x #of Liters]/1000 x (100/55)-----this is for potassium metabisulphite
For 220 gallons 74.93 g of potassium metabisulphite/62.4 g sodium metabisulphite

[Dick Dunn]

On Fri, Jan 09, 2015 at 06:47:05PM -0800, Kyle Bryant wrote:
> First off sodium metabisulphite and potassium metabisulphite have different amounts of available SO2. Sodium metabisulphite 64% available. Potassium metabisulphite 55% available. Equation I use.

[snip]

"yes, but..."
(1) It's not a huge difference.
(2) both KMS and NaMS degrade over time, depending on storage conditions,
PotM, etc. (And they probably don't degrade at the same rate under the
same conditions!)
(3) the "science" of how much to use isn't all that exact anyway, since it
depends not only on the (easily measured) pH, but on various difficult
factors which cause "binding" of SO2 so that it doesn't do any good. Dirty
or aging fruit needs more SO2.

SOoo...make it easy on yourself; mind the difference between precision and
accuracy, and don't sweat the small $#!+. Figure you get 50% SO2: a gram
of KMS or NaMS will give you half a gram of SO2, to closer than the other
factors will allow you to calculate meaningfully.

--
Dick Dunn rc...@talisman.com Hygiene, Colorado USA

[Michael Figueroa]

In his book, Charles Jolicoeur shows that when sulfiting the must *prior to fermentation* the correct amount varies somewhat depending on pH. I guess it stands to reason that the same could be said sulfiting to intervene in a fermentation.

--

Mike Fig

Tacoma, WA

[Michael Figueroa]

EDIT: In his book, Claude Jolicoeur...

Whoops

[Andrew Lea]

On 13/01/2015 15:55, Michael Figueroa wrote:

> when sulfiting the must *prior to
> fermentation* the correct amount varies somewhat depending on pH. I
> guess it stands to reason that the same could be said sulfiting to
> intervene in a fermentation.

Actually, no. Because when you use SO2 *after* fermentation you are
doing it primarily to control oxidation which is independent of pH.

The standard wine / cider industry recommendation is to maintain 30 ppm
free SO2 in storage, irrespective of pH.

Andrew Lea

--
near Oxford, UK
Wittenham Hill Cider Portal
www.cider.org.uk

[winters...@gmail.com]

So I should be shooting for 30ppm rather than 50ppm!  Thanks, Andrew.

[Andrew Lea]

On 13/01/2015 16:25, winters...@gmail.com wrote:
>
> So I should be shooting for 30ppm rather than 50ppm! Thanks, Andrew.

No. The idea is that you add 50 ppm and after a few days you end up with
30 ppm (losses due to binding and oxidation). If you want to know
exactly where you are you have to measure the free SO2 in storage and
keep an eye on it all the time to maintain that level. That's what the
professionals do.

Andrew