Hi all.

Following discussion on this in a recent thread, , Michael Pronay sent me
the text of an article which appeared in 1996.

In it, Bruno Prat is interviewed by Alain Laliberté.

Here is a digest. If anyone wants the full french text, they only have to
ask.

===================
After explaining that vines collect water by osmosis and that eliminating
excess water by saignée is an old Médoc tradition, M Prats describes the
mechanism of reverse osmosis which in effect does the same thing.

An advantage compared to vacuum evaporation is that reverse osmosis is self
regulating, in that the stronger sugar solutions need higher pressures up to
the sensible technical limit of about 60 atmospheres which would give 14° in
the finished wine.

If RO has long been known elsewhere, it has been tested on a large scale in
the Médoc since "87, Cos dEstournel since 1989 Only 5 or 6 properties did
it in 1996, because it is very expensive. In contrast, the cheaper vacuum
evaporation is relatively widespread. However if the latter is not done to
excess, the results are the same.

The technique corrects an excess of water in healthy grapes due to abundant
rain just before the harvest. It cannot make them ripe, and should never be
employed when grapes lack maturity. Thus in "91, 92, 93 & even "94 RO
showed itself invaluable. Those who didnt have it, used saignée, through
which one also loses sugar, aromatics and long colloidal molecules,
especially polysaccharides.

He regards RO, therefore as a kind of selective saignée, but carried out
before fermentation starts. They remove from 10 to 15% of the volume, which
corresponds to an increase of 1 to 1.5°. It is better than the necessary
evil of chaptalisation, he feels, because for him, removing excess water is
more natural than adding sugar. RO does not increase tartaric acid in the
finished wine, but does increase malic acid, and also makes for a fatter
wine as all polyphenols are perfectly retained, as are all yeasts and
bacteria.

As aromatic elements are less well defined anyway, the effect is harder to
judge. The rejected water can have a faintly herbaceous smell, and if
botrytrised musts are treated, the water has a faint smell of rot. Although
the water is not 100% pure, the 0.5% impurities are largely mineral salts.

He goes on to explain that in the Bordeaux region, the Cabernet Sauvignon is
often light in sugar, which has to be increased one way or another. In
America, more often problems are caused by an excess of sugar, and the
technique is useless.

If Leoville Las-Cases carries out RO on its whole crop, and not one kg of
sugar has entered the estate since 1987, in Cos, they take a middle line,
ROing 1/3 of the harvest. He predicted that they would increase this rather
than continue to chaptalise.

In "95 Merlots gave 14°, and RO was out of the question, but Cabernet
Sauvignon even in the ripest years never gets above 12.5°. In St Emilion,
although less useful due to the proportion of Merlot, perfectionists such as
LAngelus do it. Although Merlot can become diluted by rain, it can still
have too high a sugar content to be concentrated.

He pointed out that in the 19th Century Médoc wines contained 10.5°and
doubted whether the public would accept this figure today. When asked if RO
wouldnt lead to standardisation, he felt that it would improve some lesser
years but have no effect on the best. The state of maturity wouldnt be
altered, but one could eliminate dilution effects . For example the dilute
"73s made from perfectly mature grapes would have been wonderful if made
nowadays. On the other hand in "74, which was both dilute and unripe, RO
would merely have accentuated the unripeness.

Asked about the legal position, M Prats explained that it was tolerated on
an experimental basis. The French Government would press the European Union
to consider it as a precedure to be authorised.

Asked what yields they get, M Prats explained that at 10,000 vines per Ha,
St Estephe could easily give 60Hl/Ha, which he felt was viable. He doubted
that Margaux could expect more than 45Hl/Ha for decent quality.

He explained that because most manufacturers of RO equipment expected to
work on very clean water, only one manufacturer had specialised in adapting
their equipment for winery work, for example by regularly brushing the
membranes. He prefers flat membranes to fibrous ones, because they tend to
clean themselves. They have to change about 2% of them each year.

He doubted (in "96) that mobile RO machines would catch on, because the
concentration takes place on the must before fermentation starts, and
therefore has to be done quickly. With the machines they had, it took about
5 hours per 200 hl vat.

Finally he emphasized that one reason consumers love wine is because it is a
natural product. For that reason, he was deeply suspicious of adding
anything to it, and felt on the other hand that RO which simply _removed_
water, was less artificial, if more technical. He disagreed strongly with
the thinking of Australian winemakers, who are in favour of adding aromas.
On the other hand, he was unconcerned - unlike Robert Parker - about
removing matter by filtration as long as it wasnt done to excess, pointing
out that those who dont filter add things - egg white, bentonite, blood,
albumen and asked whether it was more natural to remove something or to add
something.


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

Ian Hoare > wrote:

> Following discussion on this in a recent thread, , Michael
> Pronay sent me the text of an article which appeared in 1996.
>
> In it, Bruno Prat is interviewed by Alain Laliberté.
>
> Here is a digest. [...]

Superb job, Ian!

M.

Ian,
Thanks for the translation/digest. My French is somewhat primary
and it would have taken me hours to translate.

Thanks, Ian.

Andy

Salut/Hi Michael Pronay,

le/on Tue, 08 Mar 2005 16:20:46 GMT, tu disais/you said:-

>Ian Hoare > wrote:
>
>> Following discussion on this in a recent thread, , Michael
>> Pronay sent me the text of an article which appeared in 1996.
>>
>> In it, Bruno Prat is interviewed by Alain Laliberté.
>>
>> Here is a digest. [...]
>
>Superb job, Ian!

Thanks, I'll pass your compliments on to Jacquie, whose hard work in
redlining the essential elements of the french allowed me to sort of
translate it.

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

On Tue, 08 Mar 2005 17:01:00 +0100, Ian Hoare >
wrote:

>Hi all.
>
>Following discussion on this in a recent thread, , Michael Pronay sent me
>the text of an article which appeared in 1996.
>
>In it, Bruno Prat is interviewed by Alain Laliberté.
>
>Here is a digest. If anyone wants the full french text, they only have to
>ask.
>
>===================
>After explaining that vines collect water by osmosis and that eliminating
>excess water by saignée is an old Médoc tradition, M Prats describes the
>mechanism of reverse osmosis which in effect does the same thing.

Good article.

A couple of questions:

What is saignée?

What equipment is used for RO (membranes and electricity, etc.)?


--
=================================================
Do you like wine? Do you live in South Florida?
Visit the MIAMI WINE TASTERS group at
http://groups.yahoo.com/group/miamiWINE
=================================================

Leo Bueno > wrote:

> A couple of questions:
>
> What is saignée?

Letting run off part of the (white or slightly rosé) coloured
juice of red wine prior to fermentation to augment the proportion
of solid parts vs. liquid in order to get better extraction of
colour and tannins from the skins.

M.