Yesterday I decided to titrate with NaOH to measure TA, but instead of
looking at the color change, I used an electrode pH meter to find the
end point. I'd like to show you the steps that I followed, and you can
tell me if I did it correctly.

- Calibrate the pH meter using a 7.01 buffer solution
- Heat up a sample of wine to remove CO2
- Measure 15 ml of the wine into a container
- Start titrating with NaOH (0.2 N) and measure the pH until it reaches
8.2

I used commercial wine (an Australian shiraz) for this experiment, and
the thing that confused my is that I only needed 4.3 ml of NaOH to
reach the endpoint, which means that the TA is 4.3 g/l as tartaric.
Isn't that too low? Don't commercial wines usually have TA closer to 6
g/l? Thanks in advance for your help.

I am no expert but I think you should Calibrate your PH meter with 2
buffers, PH 7 first and then PH 4. That way the meter can calibrate
the slope correctly.

andy wrote:
> I am no expert but I think you should Calibrate your PH meter with 2
> buffers, PH 7 first and then PH 4. That way the meter can calibrate
> the slope correctly.

I agree. Some other comments:

I would measure the wine before heating it to get rid of CO2. You may
have lost alcohol and or water during the heating which would
concentrate the acids. The procedure I've heard is best is to measure
the 15 ml of wine, heat and then restore the original volume using
distilled water.

4.3 g/l probably isn't out of the realm of some Australian Shiraz. Many
of them lack the acid backbone that I enjoy in wine, especially some of
the low end, early drinking wines. Did you taste the wine you tested?
Was it a bit flabby?

Andy

Andy:

Thanks for the reply. Yes, the wine was cheap and young, and didn't
taste "acidy", so maybe the 4.3 measurement was not erroneous after
all.

Maybe in order to remove the CO2 it would be better to subject it to
vacuum than to heat it up, no?

Subjecting a wine to a vacuum will still lose fluids.
Wonderful equipment you have!
Sean

I also have a question. I've already add 50grams of tartaric to a Lodi
Zin that had a pH of around 4.

I'm using 0.1N NaOH.

When I check the pH of the wine I got 3.49. I add 5ml of wine to a
flask, add 50ml of distilled water and the pH reads 3.6. What gives?
Shouldn't it be the same?

It took about 4.7 ml of NaOH to get to 8.2, so that's about .70 TA.

Igor wrote:
> Yesterday I decided to titrate with NaOH to measure TA, but instead of
> looking at the color change, I used an electrode pH meter to find the
> end point. I'd like to show you the steps that I followed, and you can
> tell me if I did it correctly.
>
> - Calibrate the pH meter using a 7.01 buffer solution
> - Heat up a sample of wine to remove CO2
> - Measure 15 ml of the wine into a container
> - Start titrating with NaOH (0.2 N) and measure the pH until it reaches
> 8.2
>
> I used commercial wine (an Australian shiraz) for this experiment, and
> the thing that confused my is that I only needed 4.3 ml of NaOH to
> reach the endpoint, which means that the TA is 4.3 g/l as tartaric.
> Isn't that too low? Don't commercial wines usually have TA closer to 6
> g/l? Thanks in advance for your help.
>

Marty Phee ) wrote:
>I also have a question. I've already add 50grams of tartaric to a Lodi
>Zin that had a pH of around 4.

>I'm using 0.1N NaOH.

>When I check the pH of the wine I got 3.49. I add 5ml of wine to a
>flask, add 50ml of distilled water and the pH reads 3.6. What gives?
>Shouldn't it be the same?

>It took about 4.7 ml of NaOH to get to 8.2, so that's about .70 TA.

Nope. The pH should go up. And it went up by only as little as it
did because wine is a pretty amazing buffer--it tends to resist pH
changes.

Remember, pH is the negative log of the hydrogen ion concentration,
so if you dilute the wine with water, you lower the concentation,
and thereby raise the pH.

Dave
************************************************** **************************
Dave Breeden

The procedure I follow is to collect a 50 ml sample; heat it, cool it
back to the original temperature, restore the lost volume (which is
almost always less than 2% of the original). Then measure both pH and
TA.

To be honest most of the texts I have do not say it is necessary to
heat the sample before measuring pH. I can tell you from experience
that if there is any dissolved CO2 in the sample it will affect both TA
and pH.

4.3 g/l does seem low, I wonder if your 0.2 N NAOH is calibrated, if
the container is open for a bit it can and will go 'off' normal.

Joe

The Procedure you follow is all correct, heating the wine to degass it
is fine, according "Techniques for Chemical Analysis and Quality
Monitoring During Winemaking".

It is possible to dilute the wine with RO water for a TA without
adverse effect. Again it reccomends it in the lab book, in order to
ensure the pH meter electrode is covered, if using small amounts of
wine.

wrote:
> The Procedure you follow is all correct, heating the wine to degass it
> is fine, according "Techniques for Chemical Analysis and Quality
> Monitoring During Winemaking".
>
> It is possible to dilute the wine with RO water for a TA without
> adverse effect. Again it reccomends it in the lab book, in order to
> ensure the pH meter electrode is covered, if using small amounts of
> wine.

Yes, as long as you measure the volume of wine before you subject it to
heating or (reasonable) dilution you should be ok.

Andy