How to Measure Acidity in Wine

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outdoorsmadness

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now i think i may be able to use my kit, you explained it better than instructions on box. i didnt know that the gray color would turn back into the original color of the must untill it reached the stopping point, well put.
thanks, Bryan
 

PPBart

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One point not made clear in the memo is the concentration of the Sodium Hydroxide solution -- what is the expected value?
 

Tom

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If you have it 18 months toss it
Personally I get a new bottle ever year to keep it fresh
 

surlees

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I think what PPBart is asking is what is the normality of the NaOH used in the TA titration?

Fred
 

PPBart

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I think what PPBart is asking is what is the normality of the NaOH used in the TA titration?

Fred
That is correct.

My question was prompted by experience -- some years ago I bought my first acid test kit, and promptly spilled most of the NaOH. I went to a local winemaking shop to get another kit and discovered that I could simply get a bottle of NaOH for much less expense. Didn't realize until later (after much confusion) that the NaOH that came with the kit was 0.2N, while the bottle I bought to replace it with was 0.1N ...
 

DesertDance

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Tom, thank you so much for this document. I have saved it in my winemaking folder on my computer. I was so confused about how to decrease acidity, and being so new at this, I thought adding sugar would help get rid of the tartness. But no, that was NOT the answer! Be right back! I have some wine to fix!!
 

sjo

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Tom,
My directions say to add the sodium hydroxide untill there is no more color change. I do get to a point where the color turns pink or grey and will not go back to the original color but adding more soloution will give a darker color. I have taken my measurements at the point where more hrdroxide will not give any more change in color.
Are there different kits out there that work differently or am I doing it wrong?
Scott
 

BobF

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A quick reference on how to check acidity in wine
Tom, great doc. I think you're missing something though. The last sentence in the section "How to Measure Acidity Using a Titration Kit" is "If you ever run out of sodium hydroxide or phenolphthalein"

That's it. It doesn't say what to do :)
Maybe it should be:
"If you ever run out of sodium hydroxide or phenolphthalein order refills."
Or:
"If you ever run out of sodium hydroxide or phenolphthalein you're out of luck."
Or:
"If you ever run out of sodium hydroxide or phenolphthalein sacrifice one 750ml bottle of your favorite wine to [insert deity of choice here]."
 

Tom

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Tom,
My directions say to add the sodium hydroxide untill there is no more color change. I do get to a point where the color turns pink or grey and will not go back to the original color but adding more soloution will give a darker color. I have taken my measurements at the point where more hrdroxide will not give any more change in color.
Are there different kits out there that work differently or am I doing it wrong?
Scott
did you add 3 drops of the color solution? I bet you didnt.
The kit should have a small bottle of color solution, syringe,glass vial and sodium hydroxide`
 

sjo

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did you add 3 drops of the color solution? I bet you didnt.
The kit should have a small bottle of color solution, syringe,glass vial and sodium hydroxide`
__________________
Funny you should ask. Yes I did add the color soloution, however I have forgotten to add it in the past and have obtained the same results with it as without.
 

Tom

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Then I would suggest to get a fresh batch of Sodium Hydroxide. I'm thinking thats what it is.
BTW was this a dark red?
 

brewtus

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did you add 3 drops of the color solution? I bet you didnt.
The kit should have a small bottle of color solution, syringe,glass vial and sodium hydroxide`
__________________
Funny you should ask. Yes I did add the color soloution, however I have forgotten to add it in the past and have obtained the same results with it as without.
sjo - Not sure how you can get the same results without the phenolphthalein being added, the phenolphthalein is what changes color at pH=8.3. Without it, you will see no color change during the titration.

You said earlier:

"My directions say to add the sodium hydroxide untill there is no more color change. I do get to a point where the color turns pink or grey and will not go back to the original color but adding more soloution will give a darker color. I have taken my measurements at the point where more hrdroxide will not give any more change in color.".

The point at which the color turns pink (white wine) or gray (red wine) and stays there (i.e. does not go back to the original color before you added any NaOH) is the end point. This is the point where you can base your T.A. calculation on. This is the color change that is being referred to, not the change in color due to the increased intensity of the pink or gray. By adding additional NaOH, you can see an increase in intensity of the pink or gray. If you base your calculations on volume of NaOH at which the intensity of pink or gray does not change any more, your total acid calculation will come out higher than it truly is.

Make sure that your NaOH bottle is tightly sealed. CO2 is a major culprit for NaOH concentration change in stored NaOH solutions over time. If the NaOH solution concentration changes, your titrations will have errors. You can always back titrate and/or standardize your NaOH solution with each use to find the true concentration, but that's alot of work and I would suggest just buying new NaOH solution every so often.
 
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I would highly recommend the pH meter method. Color changes can be affected by several factors and are especially difficult in red wines. I bought a very nice bench top model from Valley Vintner ( Part # TE-25-4221 ) and have been extremely happy with it. I gets consistent results and maintains calibration. Plus, it adds a whole new dimension of winemaker coolness to my garage.

I tried posting a link but since I am new it not only didn't let me but it deleted everything I had typed.
 

neros

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new to wine making, started a cheapo welch's and a apfelwein batchs. quick question about ph method of checking the TA, after i have added the # of drops to bring the PH to 8.2 what is done then, ei. takes 7 drops to ge to 8.2, is the TA at 70%? not sure what to do after i get the PH to the end point.... thx
 

deboard

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Tom, thanks for the great document, I've used it many times now.

I have also been confused by the titration process like a previous poster. I did add the three drops of color solution as sjo did, but what I see is this:

After a certain number of CCs of sodium hydroxide, the must changes color, but shaking it a bit will make it go back to the original color. Add more, color changes again. This time shaking it makes it ALMOST go back to the original color. Probably halfway between original color and changed color Should I stop now? Adding more, color changes again, and this time shaking still makes it go halfway back again. Not quite though. Should I keep going until it does not change back at all?

Also, are there musts that just don't work with this? For example, if there is an artificial color present? My candy cane wine had 6 cans of niagra concentrate, but the red food coloring from the candy canes made it neon pink. I never saw a color change at all, not a bit. I did it twice thinking I must have forgotten the color solution - with the same result.
 

Tom

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Yes continue till the color does not change at all. Dark reds will not work as you cant see any color change. You must dilute the reds so you can see color change
 

deboard

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Ah! I never thought of diluting it. I suppose if I dilute half and half, what I measure is also half of the actual TA of the must?
 
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