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Old 01-19-2012, 12:17 AM   #11
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As promised, I took some pH readings on various vinegars tonight. The vinegars I checked were as follows:

  1. Apple cider vinegar. Inexpensive store brand, pasteurized.
  2. Distilled white vinegar. Again, this was an inexpensive store brand.
  3. 18 year old balsamic vinegar. The good stuff. About $120/gallon from a specialty store.
  4. Red wine vinegar from Trader Joe's.
  5. Rice vinegar from Trader Joe's.

All except the balsamic indicated 5% acidity on the label.

Here are the results, from most acidic to least acidic (remember the lower the pH, the higher the acidity):
  1. Rice vinegar - 2.19
  2. Distilled white vinegar - 2.34
  3. Apple cider vinegar - 2.57
  4. Red wine vinegar - 3.02
  5. Balsamic vinegar - 3.15
What was kind of interesting (to me anyway) is that rice vinegar was the most acidic. I really find it to have a mild flavor. Apple cider vinegar fell right into the middle of the pack.

Anyway, I found it to be a fun test, in a geeky sort of way.


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Old 01-19-2012, 07:54 AM   #12
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Quote:
Originally Posted by Steve Kroll View Post
As promised, I took some pH readings on various vinegars tonight. The vinegars I checked were as follows:

  1. Apple cider vinegar. Inexpensive store brand, pasteurized.
  2. Distilled white vinegar. Again, this was an inexpensive store brand.
  3. 18 year old balsamic vinegar. The good stuff. About $120/gallon from a specialty store.
  4. Red wine vinegar from Trader Joe's.
  5. Rice vinegar from Trader Joe's.

All except the balsamic indicated 5% acidity on the label.

Here are the results, from most acidic to least acidic (remember the lower the pH, the higher the acidity):
  1. Rice vinegar - 2.19
  2. Distilled white vinegar - 2.34
  3. Apple cider vinegar - 2.57
  4. Red wine vinegar - 3.02
  5. Balsamic vinegar - 3.15
What was kind of interesting (to me anyway) is that rice vinegar was the most acidic. I really find it to have a mild flavor. Apple cider vinegar fell right into the middle of the pack.

Anyway, I found it to be a fun test, in a geeky sort of way.


I love your pH meter!!!! Bring on the geeky stuff. Where did you get it, Steve?
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Old 01-19-2012, 08:27 AM   #13
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I love your pH meter!!!! Bring on the geeky stuff. Where did you get it, Steve?
It was something I picked up at a place called Valley Vintner in San Francisco a few years ago. I originally bought it for testing wine grapes, but discovered it has a lot of other uses as well. It's a handy item to have in the kitchen at times.
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Old 01-19-2012, 08:31 AM   #14
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It was something I picked up at a place called Valley Vintner in San Francisco a few years ago. I originally bought it for testing wine grapes, but discovered it has a lot of other uses as well. It's a handy item to have in the kitchen at times.
I'll have to check around here...or just Edmund Scientifics. I'll be checking pH on everything Don't mind her, she's just weird that way...
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Old 01-19-2012, 08:50 AM   #15
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Have you explored acitity enough to help answer something? Am I right that titration percentage expresses the amount of glacial acetic acid in the solution and that pH expresses the overall acidity of the solution. So since with vinegar, we're always talking about acetic acid, is there a simple table of equivalent between percentage and pH for vinegar (and presumably for any acetic acid solution), ignoring the effects of other components in some vinegars. But I don't find such a table. Am I missing something?

I, too, was surprised by the rice vinegar. It just doesn't seem that strong from casual experience using it, and it's significantly stronger, considering the exponential definition of pH. I wonder how much effect on our perception of acidity is from other components. I would guess red wine vinegar would have its share of tannins, just as the wine does. Tannin's astringent, sourness, pucker factor, or whatever isn't too far from the sensation of acidity. Rice wine won't have any, of course.

Most references talk about rice vinegar as being milder and less acetic, but that generalization seems to be made from taste experience. It seems there are different acidities among rice vinegars (and among all vinegars that aren't shooting for a standard, like common white vinegar), which makes sense, as makers will dilute to the taste they want, and that taste may depend on other things than percentage or acid.
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Old 01-19-2012, 11:34 AM   #16
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Have you explored acitity enough to help answer something? Am I right that titration percentage expresses the amount of glacial acetic acid in the solution and that pH expresses the overall acidity of the solution. So since with vinegar, we're always talking about acetic acid, is there a simple table of equivalent between percentage and pH for vinegar (and presumably for any acetic acid solution), ignoring the effects of other components in some vinegars. But I don't find such a table. Am I missing something?
You're actually very close. The problem lies in assuming that the titration percentage on the label reflects only acetic acid. It doesn't. It's simply a way of expressing the total titratable acidity as if the only acid were acetic.

I'm by no means a chemist, though I've taken a couple of rudimentary wine chemistry classes at the university extension here. Most of my understanding therefore comes from that topic, so I'm going to use wine as an example.

When performing a simple titration, the results are always expressed as a single type of acid, even though there may be other acids present. For example, wine contains tartaric, malic, citric, acetic, succinic, lactic, carbonic, and a handful of other acids. Tartaric is the predominant acid, usually making up more than half of all the acids present. So when we titrate wine, we express the results of the titration as if all of the acid is tartaric (except in parts of Europe where, inexplicably, sulfuric is the standard). The result is calculated by plugging numbers into a formula. One constant in the formula is called the Acid Dissociation Constant (ADC), and it's different for each type of weak acid. For wine, we plug in the ADC value for tartaric acid.

When we say that a vinegar is 5% acidity, that's actually the total of all acids present in the vinegar, but it's calculated using acetic acid's ADC value. If you were to perform an analysis of apple cider vinegar, you would find it also contains a great deal of malic acid. Wine vinegar, being made from wine, contains mostly tartaric. Since distilled vinegar is manufactured using only water and grain alcohol, it's really the only vinegar where the acid profile is mostly acetic acid.

While it stands to reason that if you add acid to a solution the pH will drop, one of the things that I learned in wine chemistry class is that pH and the titratable acidity don't have any direct correlation. To illustrate, let's say that you have two containers of water. If you were to add 5 gm of phosphoric acid to one and 5 gm of lactic acid to the other, each container would contain 5 gm of acid, but the pH of the container with the phosphoric acid would have a lower pH value because phosphoric is a much stronger acid. When you start factoring in other variables like buffering capacity, it becomes a big cloudy mess.

I guess that was kind of a long answer, but I hope it helps explain why there isn't a table that says x% titratable acidity = y pH.

By the way, I think your absolutely correct about the interaction of tannin and acidity in wine vinegar. One of the things we're taught in winemaking is that a wine that's both tannic and acidic is not a pleasant wine to drink. That's why you'll find that tannic red wines have a relatively high pH as opposed to crisp white wines that have little tannin.
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Old 01-19-2012, 11:56 AM   #17
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i feel smart because i understood that...




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Old 01-19-2012, 12:06 PM   #18
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I hate trying to explain smart things, because I'm really not all that smart. I have to dumb things down to my level just to understand it myself.
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Old 01-19-2012, 12:14 PM   #19
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I just wanted to soak a bit of garlic

Seriously though, interesting stuff.....
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Old 01-19-2012, 06:07 PM   #20
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Okay. So the titration percentage is the percentage of acid the vinegar would be if all the acid was whatever standard acid was assumed. Kind of like knowing how much wood a wood chuck chucks based on the assumption that it's indeed a wood chuck chucking wood. A reasonable measure, if you know what its limitations.

(Or the version I would sometimes insert in a math test:

If a chicken and a half lays an egg and a half in a day and a half, how long would it take a three-legged grasshopper to kick all the seeds out of a watermelon?)
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