In article >,
"Paul E. Lehmann" > wrote:
> fishziblu wrote:
>
> > Hi I've just bought two tests to measure TA in wine. However both
> > tests rely on a colour change of the liquid . Due to me having a very
> > deep red wine, I am unable to measure when the transition, even if I
> > dilute it 50% with water.
> >
> > Is there any other method?, or should I abandon the TA test altogether
> > and relay on taste for acid content?
>
> No don't abandon the test. It is really quite easy if you have a pH meter.
> The color change occurs when the pH reaches 8.2. Simpley add the NaOH as
> you normally do and at the same time stir and watch your pH. The end point
> occurs when the pH is 8.2. I know, it is not real intuitive that 8.2 is
> the end point instead of 7.0 but 8.2 is the point at which the indicator
> indicates neutrality. For more information, do a google on titration and
> 8.2. I used this method for the first time last week and it works like a
> charm.
You need a burette for this test (a stir plate, and stir bar would be
helpful but not necessary). Use .1N NaOH. First boil some D.I. water
(adding some juice to the water can be helpful, but just a splash), to
drive off any dissolved CO2. Adjust about 75 milliliters of this to a pH
of 8.20. Add 10 mls of sample to the titration solution, and add .1N
NaOH until you return to a pH of 8.20. Then multiply the number of mls
of .1N NaOH you used, and multiply by .75 (another fudge factor). The
results are expressed as grams of tartaric / 100 ml.
The pH is a better indicator of the sourness of the wine. The TA can be
adjusted (by home wine makers) with the use of K2CO3 (potassium
carbonate). Calcium carbonate could also be used but it may precipitate
more tartaric than you want. Test in small batches first, and give it a
couple of weeks to stabilize.
--
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