Acid Test w/ pH meter

[pditt13]

I am new to wine making and struggle with my acid test. I have 3 wines going, cab sauv, merlot, and niagara. I gave up on the color test and bought a decent pH meter for acid testing. I don't know whether my sodium hydroxide is bad, or if i am doing something wrong. I cannot get the pH to 8.2 I added almost 20ml to my niagara and the highest it went was 4.1. Added 10ml in my reds and didn't go above 4 on the pH meter so i gave up. I don't know where to go from here. Since I am new to winemaking, my acid test kit is fairly new. I even bought another one thinking it was old, and the second kit, same results. What am i doing wrong?

 

[user 36973]

A couple things to double check... Did you buy fresh calibration standards for the pH meter? And are you using 0.1/0.2N sodium hydroxide or 0.01N?

 

[pditt13]

Yes, I bought 4.01 and 7.01 and calibrated right before test. I am using 0.1N

 

[user 36973]

How large are wine samples you are using? (I use 10ml samples and titrate using a buret into a beaker with a stir bar.)

With a 10ml wine sample, every 10ml addition of the 0.1N NaOH neutralizes 7.5g/L of acid. I would expect your reds to be around 6g/L and the Niagara to be upwards of 10g/L.

As you noted, there has got to be a miscalibration or procedural problem (I'm guessing miscalibration). Maybe the probe wasn't fully rinsed of the 4.01 solution before calibrating to 7.01? As a reality check, did you measure the pH of the wine sample and the NaOH? The wine samples should be in the 3.1 to 3.6 range while the 0.1N NaOH should be around 11.

 

[KCCam]

And if you still have strips, you could get a ball park reading of the NaOH, and the calibration solutions. That might help pinpoint if the problem is with the meter or with the solutions.

 

[pditt13]

My wine was 3.4 pH before I started adding the NaOH. I just checked my .1N and it is 11.84. Rinsed the probe well and put it in my 7.01 and it registered 7.04

 

[pditt13]

AND my wine sample was 10mL

 

[KCCam]

Maybe try the other way around? Start with, say 5 ml NaOH, and add wine a drop at a time. How quickly does the pH drop? Maybe post pics or a video of your process?

 

[KCCam]

It’s possible to test the normality of the NaOH without a meter, but you need to have 0.1 N HCl acid and Phenolphthalein indicator. Or with just the Phenolphthalein, you could titrate without using the meter. See :
www.extension.iastate.edu/wine/titratable-acidity
https://www.extension.iastate.edu/wine/titratable-acidity

 

[Rice_Guy]

* from my experience, the two vinifera wines should be reasonable if the pH is 3.4 on the must, and the niagara if it is grown up north might be high 1% ish.
* finished wines at racking still have CO2 therefore the numbers tend high.
* the general belief is that adjusting pH in the must is worth while since it will provide shelf life and TA can adjusted by taste on a finished wine, AKA balancing the sweetness
* VA ie oxidation of the alcohol to vinegar could raise the TA well above normal for the grape. Does the finished wine smell like salad dressing?

Welcome to WMT

 

[Rice_Guy]

two years ago I made a really out of balance mulberry, ,, since then I have designed TA to fit the sweetness I like on finished wine.View attachment 68474
commercial sodas, teas, juice boxes, cider, etc also will produce a sloped line, but shifted to the left. ,,, a guess is that 10 to 14% alcohol has an innate sweetness ,,, wines from others, are in this data set

 

[pditt13]

I tried the other way around. I started with 5 mL of 0.1N, ph reading 11.74 (did another calib in 7.01 then 4.01 right before). Added 1 ml of niagara and the reading was down to 4.32.

Also to the other suggestion to try with NaOH and Phenolphthalein indicator, i have tried that and that is why i bought the meter. That was just not working for me. I had 10mL of niagara, 3 drops of indicator, and when i added the NaOH nothing happened. The color did not even change for a second, and then dissolve. All the utube instructions i watch, when they add the drops of NaOH they get a brief pink/magenta color change then it goes away. Mine never does that. I am afraid my wine is bad. I just can't believe all three gallons are bad. (I only do gallons because i am learning). I enjoy this too much to give up on making wine.

 

[pditt13]

An yea, my niagara does smell a bit like salad dressing ☹

 

[KCCam]

How about trying your process with a commercial wine? That should tell you if your process is right, basically. If the same thing happens, then one or more of your solutions, or you meter, is bad. If it titrates to a reasonable number, then redo your wine. It HAS to eventually reach 8.2. Using the procedure in the link I gave you, start with 1 ml of wine. Using distilled water that's adjusted to 8.2 first allows you to use a very small volume of wine. That should give you a result with less accuracy, but using 1/10 as much NaOH.

 

[pditt13]

I think i need or order new sodium hydroxide. I opened a bottle of cabernet sauvignon from a local winery, pH 3.9. I used up 10 mL of NaOH and it only went to 4.07. And I have only had this bottle for about a month. I am pretty sure my meter is fine. I rinsed well, dipped in 4.01 and it went to 4.01, rinsed well again and dipped it in my 7.01 and it registered 7.00

 

[pditt13]

Thank you everyone for your help and suggestions. This was my first day on the forum and I plan on doing a lot of browsing at posts and hopefully learn a lot. Gonna wait for my new bottle of NaOH and try again.
Again, thank you!

 

[sour_grapes]

Welcome to WMT!

 

[user 36973]

An yea, my niagara does smell a bit like salad dressing ☹

Or it could just be niagara. IMHO, niagara doesn't make a particularly nice smelling or tasting wine. I had one niagara vine somehow make it into my chambourcin block. I picked it separately and made wine with it for kicks. Smelled awful while fermenting. Turned out 'ok' but certainly not my favorite grape.

 

[mainshipfred]

I understand you are trying to find out why the TA test is not working but is it really necessary to test for TA. I think you will find that most wineries know what the TA is but it's not a measurement they use. They simply rely on pH and quite frankly they really rely on taste not numbers. The pH just gives the amount of SO2 required to age the wine properly. This is a little off topic but a fully saturated solution of cream of tartar will have a pH of 3.55+/- .01.

 

[user 36973]

I think you will find that most wineries know what the TA is but it's not a measurement they use.

No, TA is critical for wineries to measure in order to correct acidity and balance sweet wines. The pH is also critical for the reason you mention about controlling the free sulfite levels and it can vary significantly between varietals & vintages. Both measurements are a must for careful winemaking.