air oxidation of chardonnay

air oxidation of chardonnay

Post by Stanley D. Dun » Thu, 24 Sep 1998 04:00:00



I have read that air oxidation of crushed chardonnay grapes for some
period of time prior to pressing and fermentation is a technique
commonly used in Australia, and contributes to the rich complex flavours
of the resulting wines. (The results are of course quite different from
those of the accidental oxidation of a fermented wine which results in
conversion of *** to acetaldehyde or, in some casees, acetic acid).

Does anyone have experience with this technique of deliberate oxidation
of the fruit or know of guides as to how it should be carried out?

Stan

 
 
 

air oxidation of chardonnay

Post by Brian Lundee » Thu, 24 Sep 1998 04:00:00


Quote:

> I have read that air oxidation of crushed chardonnay grapes for some
> period of time prior to pressing and fermentation is a technique
> commonly used in Australia, and contributes to the rich complex flavours
> of the resulting wines. (The results are of course quite different from
> those of the accidental oxidation of a fermented wine which results in
> conversion of *** to acetaldehyde or, in some casees, acetic acid).

> Does anyone have experience with this technique of deliberate oxidation
> of the fruit or know of guides as to how it should be carried out?

> Stan

The theory behind pre-fermentation oxidation is that the oxidized compounds
will be eliminated from the wine through the process of fermentation,
settling and racking, thereby making the wine less prone to oxidation later.
The only restriction I know of is that the must should not be sulfited, or
sulfited as little as possible. Otherwise, the sulfites will bind the
oxidized compounds and prevent their elimination. The first time I tried
this technique I had my doubts, as I stared in horror at my settling juice (
it was a white of some type) turning the color of coffee with just a drop of
milk in it. After fermentation, the color had returned to normal and there
was no hint of oxidation in the wine.

Brian

 
 
 

air oxidation of chardonnay

Post by TomS » Mon, 28 Sep 1998 04:00:00


I've been making Chardonnay for over a decade, and never use sulfite at
crush.  Any oxidation that occurs precipitates with the lees, and the
finished wine is more stable than if the must had been sulfited.  Also, the
malolactic fermentation goes much more easily if no SO2 is present, so add
SO2 only after ML is complete.

Tom S

 
 
 

air oxidation of chardonnay

Post by Baccu » Mon, 05 Oct 1998 04:00:00


I would agree to some extent,

I have used this pre oxidation step under controlled conditions. It seems to
work well on fruit of sound quality.

Fruit that contains Bortrytis, however I don't believe should ever be
treated like this- laccase, an oxidative enzyme, can take hold and once it
develops can be difficult for the new comer to control.

May I also suggest that you take wine pH into account . In as much as
laccase does enjoy an acid environment at wine pH ( 2.8-3.7) In years where
Bortrytis may be a problem I recommend SO2 additions at the crush even
though laccase can be resistant to SO2 additions and sometimes two additions
are necessary. Laccase is imparted by Bortrytis and is a very strong
oxidant- attacks monophenols, orthodiphenols and even meta and para phenols,
diamines and ascorbic acid.

What does all this mean?- well in my experience, in good vintages where
fruit is sound ,try the pre- oxidation step, it does seem to lower the
susceptibility of further oxidation in wine.

The brown that drops out is merely quinones precipating out after binding
with SO2 (if added) though they will eventually drop out anyway.But this
binding between quinone and S02 does help stabilise the quinone against
further polymerisation. Oh oxidation is not actually prevented here but the
undesirable effects of it are.
Also many people don't realise that the rate of oxidation of wine is about
100 less  than that in must anyway. So the comment that wine does not
further oxidise so readily is  (not all the time but most) a furfy- some are
sure to disagree.

When fruit is poor consider using SO2 to help protect your juice from enzyme
oxidation and non enzyme oxidation as a scavenger of Hydrogen Peroxide
 very oxidative compound). I do

I hope this is clearer to you

Regards

Backups

Quote:

>I've been making Chardonnay for over a decade, and never use sulfite at
>crush.  Any oxidation that occurs precipitates with the lees, and the
>finished wine is more stable than if the must had been sulfited.  Also, the
>malolactic fermentation goes much more easily if no SO2 is present, so add
>SO2 only after ML is complete.

>Tom S