michael wrote:

I have had some good advice from this wine group
but still remain confused about when to use
sulphite.I have successfully made some excellent
red and white wine from grapes grown in southern
England.I seem to get some very good juice (Brix
19)with a good acid balance.My good wines were
my first attempts a couple of years ago,but I
recall that they were drunk within about 12
months after harvest.My recent problems have
been with longer storage wine which
unfortunately has been without any sulphite.The
whites have become somewhat flat and with a
touch of sherry like flavour,and the reds have
lost their fruitiness and also become a little
metallic.I am sure that this is all due to
oxidation,and I certainly plan to use a minimal
amount of sulphite for this years winemaking.I
thought that I would be making organic wine,but
I have discovered that organic winemakers do use
sulphites or the complete purists do every
operation under a CO2 blanket.I certainly do not
wish to go down the CO2 route,so I am resigned
to using a minimum amount of sulphites,but I am
unclear when to use the sulphites.

I usually wash and sort my grapes and have been
letting them ferment on the natural yeasts.All
of the grapes I have processed so far have
fermented the natural(+added) sugar out
completely in a few weeks.As I understand it,the
early addition of sulphite (e.g.50ppm)is used to
kill off any remaining bacteria and suppress the
'bad' yeasts.My question is whether this
sulphite also absorbs oxygen at this early
fermentation stage,and therefore keep the juice
fresh?I thought that the CO2 given off during
the fermentation protects the wine from
oxidation,but maybe the oxygen remains to do
damage later on.So is this early sulphite
addition important?

The next question is whether to add sulphite at
the first racking stage,say after a couple of
months,when the wine is fairly fully
fermented(another 50ppm?).I understand that most
of the initial sulphite (if added) will be used
up during the fermentation process,so maybe this
is the most important addition.I probably do not
expect an MLR fermentation as most of my juices
are reasonably but not too acidic.Will this
sulphite addition protect the wine (usually
stored in glass demijohns)if I keep it for a
couple of years?

So,in summary,I am clearly suffering oxidation
problems and plan to add sulphite either

You may also be experiencing some reduction
problems. Oxidation and reduction go hand in
hand. I am not a chemist but my understand is
that it is more complex than just "oxidation".
Some of the off flavors (metallic as an example)
may be the result of reduction reactions taking
place simultaneously with the oxidation
reactions.


(i)both immediately after pressing(and then hope
the natural yeast
gets going after a delay) and then after first
racking or (ii)just after first racking

I would very much like some advice.

Best regards
Michael

There is some excellent information he

http://brsquared.org/wine/Articles/SO2/SO2.htm

Although it can look somewhat intimidating at
first glance, I think you can get the main points
without getting too involved in the science.
Just be patient and read through and then go back
and get some general information or rules of
thumb to help you out. Or, if you want to
research the issue in detail, this is a good
place to start.