Total Acid Procedure

[smokegrub]

Is there a non-titrimetric procedure to measure total acid?

 

[Luc]

Acid is measured for the following reasons:

- Acid helps the yeast at fermenting
- Acid acts as a preservation in the wine
- Acid helps balancing the taste

So if you really know there is acid in the must, the first to points
are covered.
For the last point you could go by taste

Remember the Sumerians and Romans and the rest of us Europeans
made wine for several thousands of years without any acid testing kit.

You could also search the net for resources of recipes of your particular
fruit and use these as an estimate for the acid balance in your wine.
The first year of my winemaking was without an acid test, and looking
at recipes.

Last but not least: an acid test is not overly expensive.

Luc

 

[lockwood1956]

Is there a non-titrimetric procedure to measure total acid?

I haven't seen one....that doesn't mean there isn't one though.

Why did you wish to do it without titration? (curious)

it is a really simple proceedure, you can of course use your PH meter if you have one to measure the acid levels, but you still have to add the acid that you would during titration, you just dont need the re-agents

see here

http://www.winesathome.co.uk/forum/showthread.php?t=886

the first post deals with testing acid and has a link to an info sheet, the second post deals with testing for acid using your PH meter

hope this helps
Regards
Bob

 

[smokegrub]

I have since learned that you can titrate to a pH end-point of 8.2 as an alternative.

Why? Discerning the colorimetric end-point is very difficult for me and, especially so, in a dark colored wine.

 

[lockwood1956]

I have since learned that you can titrate to a pH end-point of 8.2 as an alternative.

Why? Discerning the colorimetric end-point is very difficult for me and, especially so, in a dark colored wine.

thew link I provided also gives info on how to test to PH 8.2 instead of colour change

but if you have no PH meter then putting a drop of the test sample onto some white card after each addition of reagent can be a help, (but still not easy to tell in a very dark wine)

regards
Bob

 

[Luc]

I have since learned that you can titrate to a pH end-point of 8.2 as an alternative.

Why? Discerning the colorimetric end-point is very difficult for me and, especially so, in a dark colored wine.

Is the problem just concerning red wines or also white wines
Do you have a sight problem ??

I have 3 different methods to measure with titration and two of them
are done by diluting the must with distilled water so the color change is much easier
to detect.
Could these be of help, or do you have a serious sight problem
like color blindnes.

Luc

 

[smokegrub]

No serious color recognition problems but working with titrations in darker liquids make endpoint determinations difficult. A pH meter, on the other hand, is extremely precise and is unaffected by color or turbidity.

 

[Luc]

Have you tried the dilluting method ???

Take one part of wine, add two parts of distilled water (or 3 parts)
and then put the needed dilluted wine in the measuring tube.

Then titrate and multiply the outcome by 3 (or 4).
It is much easier to tell when the color changes if the fluid is dilluted.

Luc

 

[smokegrub]

Luc:

I come from an environmental laboratory background and my knowledge of chemistry is predominantly related to water quality--I am now retired after 40 years. That makes me more comfortable with instrumental endpoints but thanks for the suggestions.

I have only been winemaking since last August so I have much to learn and welcome any comments/suggestions you or others have to offer. I am having a blast and the more I read, the more I find I have to learn.

Please, all of you, do not hesitate to share with me from your experiences. I am just barely intelligent enough to know that I am an absolute novice at this hobby.

By the way, I uncorked 4 bottles of my second Welch's 100% Concord Grape Concentrate wine last weekend with friends--it is now 7 months old. It was a hit! I can hardly believe the difference time has made. I look forward now to its first birthday.

On another front, I activated the yeast for my dandelion wine using a mixture of citrus juice, water, sugar and yeast nutrient. The yeast was Montrachet. It started right away so I added a pint or so of the must to it and it is very happy now (12 hours later). Following church I will strain the must and do the other things called for by the recipe and pitch the yeast.

Have a great day!

 

[Luc]

I was looking to a solution for this problem, when an idea
occurred.

How about de-colorifying the wine, would that be possible ???

So I started experimenting and I did found a solution.

Go to your local drugstore and buy some active carbon.
You might even have it at home in the medicine locker.
It is used as a diarrhea stopper or general stomach soothener.
It is sold over here as pills under brand name NORIT.
Be sure you buy or use the pure active carbon sort.

For about 3 to 4 dollars you will get a mini jar here with 100
carbon pills inside and you will need about 10 of these.

You might be lucky and youe local HBS might have this
as it is used in distilling (but that is illegal of course )

Not take a glas and put a funnel in it.
In the funnel put some cloth or kitchen cleaning paper which
will work as a filter. Crush some tablets and put them in.

Now pour the red whine over the carbon. Collect it in the glass and
again pour it over the carbon. Repeat this 3 to 4 times.
It is painstaking slow but the result is fabulous.

look at the picture of processing



And the picture of the original wine and the de-colorised wine in
the titration jar.



Winemaking and chemistry is fun sometimes.
Luc Volders

PS
Now THAT's a wine isn't it.
It is my famous elderberry.

 

[Luc]

Now I thought the previous mail was a great idea.

But there is a major setback

I tried this method with a solution I made myself.
Just for testing purposes and a great story on my web-log........

Okay so I made a solution of pure water and I added 12 grams of
cirtic acid to it.
Titration showed the acidity at 12-13 so well in the range I expected.

Then I poured this solution several times over active carbon just for testing.
Mind you there was no colour in it, I was just testing what would happen....
And guess what ...........

The acidity dropped to 8

SO BEWARE

By decoloring the must with active carbon you are also lowering the
acidity
Therefore decoloring the wine for measuring acidity is no option
as long as we do not know by how much the wine will be de-acidated.....

Luc

 

[justinray111]

A lab method using pH meter

OK here is a lab method
6 METHOD

6.1 Wine

6.1.1Standardize pH meter and check that it is operating correctly - refer to the operating manual
of the particular instrument.

6.1.2De-gas all natural wines, musts and carbonated products as follows prior to measuring pit:
Transfer 70 ml sample into a large test tube and place in a waterbath at 80°C for 5 minutes.
Stopper the test tube and shake, remove the stopper and repeat till degassed. Finally place the
test tube into an ultrasonic bath to remove all excess CC>2. Place the test tube into a 20°C
waterbath and temperate. Alternatively use vacuum or ultrasonic bath.

6.1.3Pipette 25 ml of sample into the required receptacle (50 ml beaker).

NOTE: When measuring pH, samples must be brought to the same temperature as the buffers used for

calibration of the instrument.

6.1.4Determine pH as per instrument instruction.
NOTE: pH is always analyzed directly.

6.1.5Titrate to pH 7.0 with 0.1 N NaOH and record titration value.

NOTE: The pH should remain at 7.0 for at least 30 sec. The titration is not complete until this

prescription is complied with. If an automatic titrator is used, refer to the specific instruction manual.

6.1.6 Remove sample and rinse the electrode with distilled water. Continue with next sample after
taking the reading on the burette or instrument. After the last sample, rinse electrode thoroughly
with distilled water and store as prescribed by the electrode manufacturer until next analysis.

6.2 Grape juice and must

6.2.1 Grape juice products are analyzed for pH and total acidity exactly as for wine including the
precautions to be taken when analyzing carbonated products or where products contain residual
CO2 gas (refer 6.1).

6.2.2Juice from freshly crushed grapes (referred to as "must") contains considerable amounts of
dissolved and suspended solids, which could harm or block the electrode membrane or otherwise
interfere with the titration. Therefore, for a more accurate analysis, a sample of fresh must
obtained from the sampler at grape intake should be filtered before analysis i.e. through a
Milborrow Milk Filter or equivalent. A 25 ml sample, whether filtered or not, is analyzed
further in exactly the same manner as wine (refer 6.1).

7 RESULTS

7.1 Equivalent weight of lactic acid = 75

7.2 Titratable acid as tartaric acid (g/1) = V x 0.1 x 75 = V x 0.3

v where: V = titration volume

v = sample volume (25ml)

NOTE: Refer to Appendix A for conversion factors to other organic acids.

8. APPENDIX

APPENDIX A

The titratable acidity is sometimes expressed in terms of other acids. Values can be converted from

one acid to another by multiplying a value with the following factors:



EXPRESSED AS:
TARTARIC
MALIC
CITRIC
LACTIC
SULFURTC
ACETIC

Tartaric
1.000
0.893
0.853
1.200
0.653
0.800

Malic
1.119
1.000
0.955
1.343
0.731
0.896

Citric
1.172
1.047
1.000
1 .406
0.766
0.938

Lactic
0.833
0.744
0.711
1.000
0.544
0.667

Sulphuric
1.531
1.367
1.306
1.837
1.000
1.225

Acetic
1.250
1.117
1 .067
1.500
0.817
1.000