Salut/Hi Andy,

le/on 5 Mar 2005 18:04:18 -0800, tu disais/you said:-


>Mike Tommasi wrote:
>> On 5 Mar 2005 09:33:32 -0800, "AyTee" > wrote:

>> >Can that be true? Sugar more expensive than RO? I have no particular
>> >objection to RO, but it is my understanding that it is an expensive
>> >process.

>> Apparently not, otherwise you would not have over 600 of these things
>> in France's top two wine areas.

I don't know whether 600 machines in the thousands of estates counts as a
significant but I do know that their usage is "tolerated" not encouraged.
However, in a year where rain during harvest has diluted the crop, and where
otherwise chaptalisation would have to be practiced to increase the alcohol
level, I can understand the temptation.

>I understand reverse osmosis is used more than most winemakers are
>willing to admit,

Grinm. All sorts of things are done mucxh more than most winemakers are
willing to admit!!!

> and that it is usually used to remove volatile acidity, or to decrease alcohol concentration to below 14 percent for
>tax purposes. In America, that is --

Really? This is an entirely different usage from that practiced here, and
I'm not clear how this can be done. Sounds like a question for Mark!!!

Trying to keep technicalities to a minimum, reverse osmosis is like
operating a filter. You take a semi permeable membrane, which lets small
molecules through but not larger ones, and force the liquid being treated
through it. It's most common usage is for desalination, where it allows H2O
through but not Na+ and Cl-. I would be utterly astonished if a "normal"
semi permeable membrane could allow volatile acidity (acetic acid CH3C00H)
and alcohol (ethanol, C2H5OH) through _without_ letting through the water in
much larger quantities. I have given the chemical formulae, because in
general the more complex the structure (and the higher the atomic weight of
the elements composing the molecule) the larger it is, and the more
difficult it will be to pass them through the pores of the filter. Now it's
obvious that these two chemicals with two carbon atoms each will be bigger
than water with only one oxygen atom. So forgive me if I am doubtful about
whether you're right.

> Europe may be different. Can it also be used to increase alcohol?

Indeed it can, or rather, it can be used to _remove water_, which is
slightly different in essence, and why it could be considered a "better"
solution to difficult years than chaptalisation.

Think about it. Adding sugar does nothing but adding alcohol. It can easily
throw the wine out of balance as it won't increase any of the components of
flavour.

Removing part of the water simply makes a more concentrated wine, almost as
if the vines had received less water in the run up to harvest. Before
everyone (and Mike T especially) jumps on me for this, I hasten to add that
it's not going to give results that are always better. BUT, as I said at the
beginning, in years where the harvest has been diluted by rain during
picking, it could very well play a part. I'm thinking of the notorious '64
vintage in Bordeaux. This was a year where some Chateaux were able to
complete their pickings in dry conditions and made magnificent wines. Others
were caught by the rain, the must was diluted and the wines were not so
good. Some tried to over-chaptalise their way out of it, and gave "hot"
wines. Others simply had dilute wines. If they had had R.O, it is very
probable that they would have been able to make a better tasting wine.

Note that I'm not expressing an opinion as to whether it's a "good thing" or
not, I'm simply trying to explain how R.O. works and therefore what it can
and can't do.

--
All the Best
Ian Hoare
http://www.souvigne.com
mailbox full to avoid spam. try me at website