This question gets increasingly complicated.

I often end up with wines that have pH's that are either too high or
too low, and the best solution is to blend the two. My question is how
to predict the resultant pH.

Obviously, pH is a log function, so blending equal parts of wines with
pH's of 3 and 4 DOESN'T produce a wine with a pH of 3.5. A wine with a
pH of 3 has 10 times the concentration of H+ ions than a pH of 4. Does
anyone know of an equation to predict a resultant pH of a blended wine
the following 4 variables:

X = volume of wine with pH of A
Y = volume of wine with pH of B

My goal is to work backwards and aim for a specific pH, knowing the
pH's of the original components and then calculating the necessary
volumes of the two components. While bench trials are another
solution, there should be some science to predict the results.

Thanks for your help,

Lee

Lee wrote:
> This question gets increasingly complicated.
>
You're not kidding ...

> I often end up with wines that have pH's that are either too high or
> too low, and the best solution is to blend the two. My question is how
> to predict the resultant pH.
>
Sure, it can be done ...

> Obviously, pH is a log function, so blending equal parts of wines with
> pH's of 3 and 4 DOESN'T produce a wine with a pH of 3.5. A wine with a
> pH of 3 has 10 times the concentration of H+ ions than a pH of 4. Does
> anyone know of an equation to predict a resultant pH of a blended wine
> the following 4 variables:
>
> X = volume of wine with pH of A
> Y = volume of wine with pH of B
>
> My goal is to work backwards and aim for a specific pH, knowing the
> pH's of the original components and then calculating the necessary
> volumes of the two components. While bench trials are another
> solution, there should be some science to predict the results.
>
> Thanks for your help,
>
> Lee

pH = pKa + log([conc high pH]/[conc low pH])

http://www.changbioscience.com/calcu...asselbach.html

I'm an unemployed chemist, so conceptually, this is an easy topic for
me. But ...
1) You use conc of the acid and base, not the pH to determine how much
of each

2) You need the value for pKa, which is a constant. Now, that number
is published for citric, malic, and tartric acids, but what about the
other acids, and how much of each. You can't know this without an
expensive lab test.

3) Here's my question: Do you really need to get an exact final pH to
make the wine the proper flavor and stability?

I figure, you're just going to have to use trial and error to get to
where you want.

That is fine and all, but you also have the problem with different
buffer systems (the Henderson-Hasselbach equation is for determining pH
in a buffer system, if the acid/base does not buffer but instead
completely disociates in water like HCl then [H] = [HCl] and pH = -log
[HCl] - for the non chemists). So you have multiple pKas to deal with.
You have bicarbonate buffers, phosphate buffers and several organic
acid buffers (tartaric, malic, acetic, succinic, citric and more).

You could make the assumption that the dominate acid will determine the
final pH, in in use you will find that assumpion does not work that
well.

Mathematically the answer is yes. You can use the Pearson's Square -- but
not exactly as it is normally used. As you comment, the pH scales are log
based. So first you need to take the exponent of each pH. Then use the
Pearson's Square. Then take the log of the final number.

There are "got'chus" however. pH is not going to blend like alcohol. As
commented above, the different buffer systems and different acids that will
interact differently when the wines blend will change the pH. You might
blend them and check the pH and find it is quite far off from the predicted
value. In fact you might blend them and check the pH and then check it
again a week later and find that it has changed considerably from the first
measure.

It might work but I am not sure it is valid to talk about blending pH.

Ray

"Lee" > wrote in message
oups.com...
> This question gets increasingly complicated.
>
> I often end up with wines that have pH's that are either too high or
> too low, and the best solution is to blend the two. My question is how
> to predict the resultant pH.
>
> Obviously, pH is a log function, so blending equal parts of wines with
> pH's of 3 and 4 DOESN'T produce a wine with a pH of 3.5. A wine with a
> pH of 3 has 10 times the concentration of H+ ions than a pH of 4. Does
> anyone know of an equation to predict a resultant pH of a blended wine
> the following 4 variables:
>
> X = volume of wine with pH of A
> Y = volume of wine with pH of B
>
> My goal is to work backwards and aim for a specific pH, knowing the
> pH's of the original components and then calculating the necessary
> volumes of the two components. While bench trials are another
> solution, there should be some science to predict the results.
>
> Thanks for your help,
>
> Lee
>

"Huh?" Might you chemists pls dumb down the discussion for us scientifically
impaired readers? Simple english preferred.... among the challenged,
bobdrob.


"Ray Calvert" > wrote in message
...
> Mathematically the answer is yes. You can use the Pearson's Square -- but
> not exactly as it is normally used. As you comment, the pH scales are log
> based. So first you need to take the exponent of each pH. Then use the
> Pearson's Square. Then take the log of the final number.
>
> There are "got'chus" however. pH is not going to blend like alcohol. As
> commented above, the different buffer systems and different acids that
> will interact differently when the wines blend will change the pH. You
> might blend them and check the pH and find it is quite far off from the
> predicted value. In fact you might blend them and check the pH and then
> check it again a week later and find that it has changed considerably from
> the first measure.
>
> It might work but I am not sure it is valid to talk about blending pH.
>
> Ray
>
> "Lee" > wrote in message
> oups.com...
>> This question gets increasingly complicated.
>>
>> I often end up with wines that have pH's that are either too high or
>> too low, and the best solution is to blend the two. My question is how
>> to predict the resultant pH.
>>
>> Obviously, pH is a log function, so blending equal parts of wines with
>> pH's of 3 and 4 DOESN'T produce a wine with a pH of 3.5. A wine with a
>> pH of 3 has 10 times the concentration of H+ ions than a pH of 4. Does
>> anyone know of an equation to predict a resultant pH of a blended wine
>> the following 4 variables:
>>
>> X = volume of wine with pH of A
>> Y = volume of wine with pH of B
>>
>> My goal is to work backwards and aim for a specific pH, knowing the
>> pH's of the original components and then calculating the necessary
>> volumes of the two components. While bench trials are another
>> solution, there should be some science to predict the results.
>>
>> Thanks for your help,
>>
>> Lee
>>
>
>

bobdrob wrote:
> "Huh?" Might you chemists pls dumb down the discussion for us scientifically
> impaired readers? Simple english preferred.... among the challenged,
> bobdrob.
>

Don't worry about it. Just use Jack Keller's calculators over here.
http://winemaking.jackkeller.net/blending.asp He wouldn't steer us
wrong.

Interestingly, the only one of Jack Keller's conversion calculators
that DOESN"T work (i.e., when you enter the numbers and click "submit",
nothing happens) is the one for predicting pH. Maybe Jack (whose
advice I take as gospel) knows that this isn't a simple conversion.

Lee

Lee wrote:
> Interestingly, the only one of Jack Keller's conversion calculators
> that DOESN"T work (i.e., when you enter the numbers and click "submit",
> nothing happens) is the one for predicting pH. Maybe Jack (whose
> advice I take as gospel) knows that this isn't a simple conversion.
>
> Lee

Yeah, I just found that link on Google when I searched the question, so
I just posted it blindly. The values for pH should be on a log
scale, and they are affected by relative amounts of the various acids
in wine. I completely missed the concept of buffers in wine, maybe
they're there, maybe not, I don't know for sure. Then there's the
alcohol, that removes some of the acid's activity, and shifts the whole
mix closer to neutral. They why when you test a finished wine with a
pH meter, you should heat lightly to boil off some alcohol.

Bah. If the two wines are similar in type, and likely have the same
levels of various acids, mixing them might produce the correct pH. The
logs cancel out, don't they? If I'm wrong, just call it a brain fart
and move on ...

No one's answered my question. Does anyone really need to get the pH
value of their wine that tight? Most websites recipies and winemaking
books suggest just adding some acid mix or potassium carbonate to move
the pH down or up, respectively, or mixing over acid and over alkaline
wines, as the flavor of the wine requires it. Does anyone really get
their pH to exactly 3.5 or whatever?

I made a batch of Welches wine last March. I put a little too much
lemon juice and rind in, and it was very tart when bottled in June --
perhaps only good as a marinade. I tasted some today, its mellowed a
lot -- just like conventional wisdom said it would. So I figure I was
right to not sweat the pH with this wine.

With all deference to the scientists who have already replied, why not
use a simple bench trial to determine the desired belnd proportions?
Take a known quantity of Wine 1, measure the pH. Add a known quantity
of Wine 2, blend, and test pH. Increment until you get to the desired
level.

I use a Pearson square to give a rough indication, then start from a
more conservative assumption, adding incremental amounts of Wine 2
until reaching the desired blend acidity.

If you blend two different' pH wines, will the new pH necessarily be in
between the 2 initial pH's ?

In article .com>, CJ
> writes
>If you blend two different' pH wines, will the new pH necessarily be in
>between the 2 initial pH's ?
>
Yes, if they are in equal quantities.
--
Alan Gould. North Lincolnshire, UK.

"CJ" > wrote in message
oups.com...
> If you blend two different' pH wines, will the new pH necessarily be in
> between the 2 initial pH's ?
>
>
Probably. It will be unless the blending brings about a chemical reaction
or changes the buffering capabilities which could cause it to be outside the
original range. That said, I would expect it to be between. But I would
not blend a lot of wine without benchmarking it.

Ray