> > Several of my reds have pH's around 3.5 or so and TA's from 6.5 to
> > 7.5g/l. They are 10 months old and have not yet been cold stabilized.
> > Tastes are tart but OK with the exception of the amarone (TA 7.5)
> > which is tart like a lemon. I'd like to reduce both TA and pH in all
> > of these reds.
>
> First off, those sound like pretty reasonable numbers for a red wine, but
> I'm confused. If you reduce the pH the wine will become even _more_ tart.
>
This is not necessarily true. The TA is quite a bit more impactive on
the organoleptic qualities of the wine than pH will ever be. If you
can succeed in lowering both, the wine can become considerbly less
tart.
As David pointed out, cold stabilization of this wine will lower both.
If the pH is above 3.65, the pH will raise from tartrate
precipitation. How much of a change is highly dependent on the
specific concentrations of the various acids of the wine and is
therefore unpredictable. With that said, I've had TA's drop as much
as a gram per liter from tartrate precipitation. pH may drop by 0.15 a
best. The level of pH when tartrates are forming is a factor for how
much it will change. The further away from the wines pKa (typcially
around 3.65) the more dramatic the change.
Making wine at high pH is a dicey proposition at best. This is the
first thing Clark Smith will say when lecturing on the subject. (I
just sat through another of his lectures a couple weeks ago). Even
when conditions are proper, there can be premature browning of the
wine. And where hybrids are concerned, it's no-man's land, as more
than likely, there are not substantial tannin levels to have the wine
keep for very long at all. Sulfites at these elevated pH's is
virtually useless.
Red wines with TA in the 6.5 range should not be terribly tart. If
they are, then I'd have to question the measurements accuracy.
> > Should I just cold stabilize
This would help considerbly. Also, you don't mention whether or not
the wines are ML pos. Depending on the malate content, this could
take the pH above confortable levels for sulfite use.
>>or reduce acids with KHCO3 for example
> > and then cold stab?
>
> Your best bet is to do a bench trial on a small sample before touching the
> main lot. Put some in a small plastic soda bottle (not completely full),
> squeeze all the air out and cap it tightly. Put it into the freezer
> overnight and then let it sit in the refrigerator until it thaws. That'll
> precipitate the excess tartrates. Decant the wine from the sediment and
> taste it after it comes to room temperature.
>
> Don't worry about the numbers; concentrate on what it _tastes_ like. If
> it's still too acidic, try adding a little carbonate, shaking to release the
> CO2 and repeating the above.
>
> > Also, different sources suggest different ideal TA's for finished dry
> > reds. Pambianchi on page 83 suggests 4.0-5.5g/l. Don Buchan's
> > excellent FAQ site http://www.malak.ca/rcw.faq suggests 6.5g/l. I
> > know taste is the ultimate authority but what should I be aiming for
> > here?
>
I like my reds in the 5.0 to 6.5 range, but you've got the right idea
that the taste is the ultimate tell tale.
clyde
Steelville, MO, USofA