Ph & TA for merlot 2nd run

Ph & TA for merlot 2nd run

Post by Greg » Wed, 11 Oct 2000 04:00:00



Hello.  I rember a discussion a while back about the relationship
between Ph and TA but I can't seem to find it.

I started a 2nd run from my Merlot grapes on Friday night.  The starting
ph was 2.9 and the TA was .45%.  Those numbers seem way out of whack to
me?  Is that possible?

Anyway, it's almost through primary fermentation and the Ph is now 3.3.
I didn't test the TA.

Do you think this needs adjusting?  Or do you base everything off of TA?

Regards,

Greggg

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Ph & TA for merlot 2nd run

Post by Zinfu » Wed, 11 Oct 2000 04:00:00




Quote:

> Hello.  I rember a discussion a while back about the relationship
> between Ph and TA but I can't seem to find it.

> I started a 2nd run from my Merlot grapes on Friday night.  The
starting
> ph was 2.9 and the TA was .45%.  Those numbers seem way out of whack
to
> me?  Is that possible?

> Anyway, it's almost through primary fermentation and the Ph is now
3.3.
> I didn't test the TA.

> Do you think this needs adjusting?  Or do you base everything off of
TA?

> Regards,

> Greggg

> Sent via Deja.com http://www.deja.com/
> Before you buy.

Gregg,
What did you use for a base for the second run?  Those numbers sound
out of whack to me to.  Are sure you tested correctly?
1. what type of pH meter did you use?  Was it calibrated?
2. How did you perform your acid test?

It's hard to call if your numbers are right.  You should have
acidulated to at least .55, however your pH would have dropped even
lower and 2.9 is about as low as you would want it.  You might try
acidifying up now that your pH has gone up.  You could keep everything
as is, but at that low level of acid, you will end up with a very flat
wine.  At this point I would say taste it, and see how it tastes and
feels on the pallate. Also remeber your results will be off if you
didn't bring your sample to the boiling point and cooled before your
tests.  You need to blow off the Co2, which causes false readings.
If your acid is still as low and *accurate*, then acidulate.  I am not
sure if it would be better to do it now or wait until after
fermentation, someone else here would know better about that than I
would.  I haven't had to do that kind of thing yet.  If you were using
my recipe with water and unpressed grapes, everything should have been
fine.

cheers,
Zinful
--
If all the world's a stage,
then where's the audience sitting?

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Ph & TA for merlot 2nd run

Post by SchlossGois » Wed, 11 Oct 2000 04:00:00



Quote:
> Hello.  I rember a discussion a while back about the relationship
> between Ph and TA but I can't seem to find it.

> I started a 2nd run from my Merlot grapes on Friday night.  The starting
> ph was 2.9 and the TA was .45%.  Those numbers seem way out of whack to
> me?  Is that possible?

-----------------------

Hi Gregg:

Given the naturally occuring acids in grapes, I do not think that it is
possible to have a pH of 2.90 with an acid concentration of only 4.5g/L.

IOW, unless you added a small amount of a very powerful foreign acid to the
must, I would bet that either the TA, or the pH, or both are off.

-------------------------

Quote:
> Anyway, it's almost through primary fermentation and the Ph is now 3.3.
> I didn't test the TA.

> Do you think this needs adjusting?  Or do you base everything off of TA?

-------------------------

Testing pH & TA during an active fermentation is a ***shoot.

How does the wine taste?

If the pH is in the safe range of 3.25 -3.55 & the wine tastes fine, I would
do nothing except allow the wine to finish its primary & malo-lactic
fermentations.

Hope this Helps.

Prosit:
Ed
--
The Viticulture FAQ & Glossary - http://www.FoundCollection.com/

          "I like on the table, when we're speaking,
           The light of a bottle of intelligent wine."
                              -Pablo Neruda

 
 
 

Ph & TA for merlot 2nd run

Post by Greg » Wed, 11 Oct 2000 04:00:00


I added 46oz of Merlot concentrate (Sun Country) and about 10 lbs sugar.
I also added 2oz of Acid Blend.  The SG at start was 1.100 ( or about ).

I was using a digital Ph meter ( I forgot the brand ), but it is
supposed to be accurate to the .1.  I did calibrate it with ph 7 and ph
4 buffer solution before testing both times.
For the acid titration, I used a kit consisting of a syringe and 10%
NaOh solution.  Following the directions, I added about 4.5ccs of NaOh
to my 10cc of wine before I got the color change from the indicator.
According to the dirs, that should be .45% TA as expressed by Tartaric
Acid (If I remember correctly - It's at home and I'm not ).

The kicker is: I didn't boil off any CO2 before I tested last night.
How does the CO2 effect ph?  Is there some carbonic acid in there or
something?  Wouldn't that give the Ph reading a falsely lower number,
indicating more acidity?

I haven't sulphited yet and am getting worried, but I don't want to kill
off the yeast if it's still fermenting.... :)

Quote:

> Gregg,
> What did you use for a base for the second run?  Those numbers sound
> out of whack to me to.  Are sure you tested correctly?
> 1. what type of pH meter did you use?  Was it calibrated?
> 2. How did you perform your acid test?

> It's hard to call if your numbers are right.  You should have
> acidulated to at least .55, however your pH would have dropped even
> lower and 2.9 is about as low as you would want it.  You might try
> acidifying up now that your pH has gone up.  You could keep everything
> as is, but at that low level of acid, you will end up with a very flat
> wine.  At this point I would say taste it, and see how it tastes and
> feels on the pallate. Also remeber your results will be off if you
> didn't bring your sample to the boiling point and cooled before your
> tests.  You need to blow off the Co2, which causes false readings.
> If your acid is still as low and *accurate*, then acidulate.  I am not
> sure if it would be better to do it now or wait until after
> fermentation, someone else here would know better about that than I
> would.  I haven't had to do that kind of thing yet.  If you were using
> my recipe with water and unpressed grapes, everything should have been
> fine.

> cheers,
> Zinful
> --
> If all the world's a stage,
> then where's the audience sitting?

> Sent via Deja.com http://www.deja.com/
> Before you buy.

Sent via Deja.com http://www.deja.com/
Before you buy.
 
 
 

Ph & TA for merlot 2nd run

Post by Zinfu » Thu, 12 Oct 2000 04:00:00




Quote:

> I was using a digital Ph meter ( I forgot the brand ), but it is
> supposed to be accurate to the .1.  I did calibrate it with ph 7 and
ph
> 4 buffer solution before testing both times.

_____________________________________________________________________

It's hard to say how accurate your pH readings are, you should be using
a pH meter with an accuracy of .01 and as Ed stated, testing during
fermentation is a ***shoot.  If you want specifics on how the Co2
effects your results, I would let someone else explain.  I'm not very
scientific, or you can do a search for boiling must, and I'm usre some
of the recent discussions will pop up.  We were discussing that just a
couple of weeks ago.
___________________________________________________________________

Quote:
> For the acid titration, I used a kit consisting of a syringe and 10%
> NaOh solution.  Following the directions, I added about 4.5ccs of NaOh
> to my 10cc of wine before I got the color change from the indicator.
> According to the dirs, that should be .45% TA as expressed by Tartaric
> Acid (If I remember correctly - It's at home and I'm not ).

___________________________________________________________________

Assuming that was your pre-fermentation reading, then your pH had to be
higher than what you were reading.  Using the color change method with
red wine is too much of a pain in the arse. Try using the end point of
8.2 pH with your pH meter and using the NaOh from your acid test kit,
and Ed's formula on a previous thread. (do a search for that too)Unless
Ed reads this and can direct you to it. Do this post fermentation.
Sorry to tell youto do searches, but I am at work, don't have my notes,
and don't have time to do the searches ;-( I kinda have to do some work.
___________________________________________________________________

Quote:
> I haven't sulphited yet and am getting worried, but I don't want to
kill
> off the yeast if it's still fermenting.... :)

Don't worry about the sulphite.  With your pH being so low, you should
be fine.  taste your must, and let it tell you what it needs.  Finish
fermentation, conduct your tests again.  As far as sulphiting, when I
did my last second run, I didn't add any sulphite to the first
fermentation, until after MLF and didn't add any to the second, until
after MLF.  The only thing that went slightly wrong, was, The must of
the second run started getting that deisel fuel smell right near the
end of fermentation.  I figured the grape skins were starting to go bad
from no sulphite.  I pressed, transferred, and everything smelled just
fine in a couple of days.  I gambled by not adding any sulphite until
after MLF, and it payed off. I got an immediate, natural ML,
innoculated it with a commercial ML bacteria, and everything else went
normal.  I will be bottling it probably this weekend if my corker shows
up.

cheers,
Zinful
--
If all the world's a stage,
then where's the audience sitting?

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Ph & TA for merlot 2nd run

Post by David C Breed » Thu, 12 Oct 2000 04:00:00


Quote:



>> I was using a digital Ph meter ( I forgot the brand ), but it is
>> supposed to be accurate to the .1.  I did calibrate it with ph 7 and
>ph
>> 4 buffer solution before testing both times.
>_____________________________________________________________________
>It's hard to say how accurate your pH readings are, you should be using
>a pH meter with an accuracy of .01 and as Ed stated, testing during
>fermentation is a ***shoot.  If you want specifics on how the Co2
>effects your results, I would let someone else explain.  I'm not very
>scientific, or you can do a search for boiling must, and I'm usre some
>of the recent discussions will pop up.  We were discussing that just a
>couple of weeks ago.

CO2 is weakly acidic.  Its presence will affect a TA reading, but not
really affect the pH.  Because it is such a weak acid, and becuase
wine is so highly buffered, a little CO2 won't have much effect on pH.

Quote:
>cheers,
>Zinful

Dave
****************************************************************************

 
 
 

Ph & TA for merlot 2nd run

Post by SchlossGois » Thu, 12 Oct 2000 04:00:00




Quote:

> CO2 is weakly acidic.  Its presence will affect a TA reading, but not
> really affect the pH.  Because it is such a weak acid, and becuase
> wine is so highly buffered, a little CO2 won't have much effect on pH.

--------------------------

Hi All:

Dave is right on target.  The pKa of carbonic acid is 6.80.  It is an acid,
but just barely.  Therefore, it will increase the TA (sometimes drastically)
because TA measures the acid concentration & not strength, while it can have
a minimal affect on the pH (by _increasing_ it).

Thanks.

Prosit:
Ed
--
The Viticulture FAQ & Glossary - http://www.itsmysite.com/vitfaq

          "I like on the table, when we're speaking,
           The light of a bottle of intelligent wine."
                              -Pablo Neruda

 
 
 

Ph & TA for merlot 2nd run

Post by David C Breed » Thu, 12 Oct 2000 04:00:00


Quote:



>> CO2 is weakly acidic.  Its presence will affect a TA reading, but not
>> really affect the pH.  Because it is such a weak acid, and becuase
>> wine is so highly buffered, a little CO2 won't have much effect on pH.

>--------------------------
>Hi All:
>Dave is right on target.  The pKa of carbonic acid is 6.80.  It is an acid,
>but just barely.  Therefore, it will increase the TA (sometimes drastically)
>because TA measures the acid concentration & not strength, while it can have
>a minimal affect on the pH (by _increasing_ it).
>Thanks.
>Prosit:
>Ed

Hi Ed,

Do you know why CO2 acts to *increase* wine's pH, rather than decrease
it, as other acids do?

Dave
****************************************************************************

 
 
 

Ph & TA for merlot 2nd run

Post by SchlossGois » Thu, 12 Oct 2000 04:00:00




Quote:
> Hi Ed,

> Do you know why CO2 acts to *increase* wine's pH, rather than decrease
> it, as other acids do?

> Dave

--------------------

Hi Dave:

Here is how this phenomenon was explained to me:

The introduction of a high volume of a very weak acid (such as the carbonic
acid introduced as a byproduct of fermentation) into a wine increases the
overall gram-atom per liter concentration of acids, but at the same time its
introduction _decreases_ the overall hydrogen ion (H+) concentration within
the now expanded acidic solution.

As a result, the "H+ gram-atoms per liter concentration" goes down & the pH
goes up.

OTOT, when stronger acids are introduced (tartaric, for example), they have
a very minimal affect on the overall volume of the gram-atom per liter
concentration, while at the same time drastically increasing the overall
hydrogen ion (H+) concentration in the expanded acidic solution.

As a result, the "H+ gram-atoms per liter concentration" goes up & the pH
takes a nose dive.

Can any Chemisits help me out here?  I admit to being a grape farmer who has
ventured far out of his vineyard on this one. :-)

Prosit:
Ed
--
The Viticulture FAQ & Glossary - http://www.itsmysite.com/vitfaq

          "I like on the table, when we're speaking,
           The light of a bottle of intelligent wine."
                              -Pablo Neruda

 
 
 

Ph & TA for merlot 2nd run

Post by JohnsonT » Thu, 12 Oct 2000 04:00:00


I'm no chemist, but maybe this answer (guess) makes intuitive sense:

Example:  A wine with no CO2 has a pH = 3.4.  You now introduce CO2 with a pH
of 6.8.  Blending should raise your pH 3.4 wine to something higher due to the
higher pH of CO2.  That seems why the CO2 could raise your pH instead of lower
it, even though it is an acid (although barely).

Make sense to others?


Quote:
> Hi Ed,

> Do you know why CO2 acts to *increase* wine's pH, rather than decrease
> it, as other acids do?

> Dave

--------------------

Hi Dave:

Here is how this phenomenon was explained to me:

The introduction of a high volume of a very weak acid (such as the carbonic
acid introduced as a byproduct of fermentation) into a wine increases the
overall gram-atom per liter concentration of acids, but at the same time its
introduction _decreases_ the overall hydrogen ion (H+) concentration within
the now expanded acidic solution.

As a result, the "H+ gram-atoms per liter concentration" goes down & the pH
goes up.

OTOT, when stronger acids are introduced (tartaric, for example), they have
a very minimal affect on the overall volume of the gram-atom per liter
concentration, while at the same time drastically increasing the overall
hydrogen ion (H+) concentration in the expanded acidic solution.

As a result, the "H+ gram-atoms per liter concentration" goes up & the pH
takes a nose dive.

Can any Chemisits help me out here?  I admit to being a grape farmer who has
ventured far out of his vineyard on this one. :-)

Prosit:
Ed
--

 
 
 

Ph & TA for merlot 2nd run

Post by David C Breed » Thu, 12 Oct 2000 04:00:00


Quote:



>> Hi Ed,

>> Do you know why CO2 acts to *increase* wine's pH, rather than decrease
>> it, as other acids do?

>> Dave
>--------------------
>Hi Dave:
>Here is how this phenomenon was explained to me:
>The introduction of a high volume of a very weak acid (such as the carbonic
>acid introduced as a byproduct of fermentation) into a wine increases the
>overall gram-atom per liter concentration of acids, but at the same time its
>introduction _decreases_ the overall hydrogen ion (H+) concentration within
>the now expanded acidic solution.
>As a result, the "H+ gram-atoms per liter concentration" goes down & the pH
>goes up.
>OTOT, when stronger acids are introduced (tartaric, for example), they have
>a very minimal affect on the overall volume of the gram-atom per liter
>concentration, while at the same time drastically increasing the overall
>hydrogen ion (H+) concentration in the expanded acidic solution.
>As a result, the "H+ gram-atoms per liter concentration" goes up & the pH
>takes a nose dive.
>Can any Chemisits help me out here?  I admit to being a grape farmer who has
>ventured far out of his vineyard on this one. :-)
>Prosit:
>Ed

Well, I'm a chemist, or at least I play one at work.  :-)

It's still not clear to me *why* the overall hydogen ion
concentration, which is what pH measures, would be *decreased* upon
the addition of an acid.

Maybe the key is in your words "now expanded" above--maybe the CO2
increases the volume of solution by such an extent that it effectively
lowers the hydrogen ion concentration.  If so, though, I would have
thought that that would lower TA as well, which is also a measure of
concentration.

Weird.

Dave
****************************************************************************

 
 
 

Ph & TA for merlot 2nd run

Post by David C Breed » Thu, 12 Oct 2000 04:00:00


Quote:

>I'm no chemist, but maybe this answer (guess) makes intuitive sense:
>Example:  A wine with no CO2 has a pH = 3.4.  You now introduce CO2 with a pH
>of 6.8.  Blending should raise your pH 3.4 wine to something higher due to the
>higher pH of CO2.  That seems why the CO2 could raise your pH instead of lower
>it, even though it is an acid (although barely).
>Make sense to others?

Hi,

That's intuitively appealing, but I don't think it can be right.  To
raise the pH of a solution, you must do one of two things:  either
lower the number of hydrogen ions in solution, or increase the volume
of solution while keeping the number of hydrogen ions the same.

If you keep the volume of a solution the same but add acid, you have
to decrease the pH.  It could be I suppose, but I don't think it is,
that addition of CO2 lowers the hydrogen ion concentration by shifting
the pKa's of the other acids and making them less acidic.  But if that
were true (if adding acids caused acids already in solution to be less
acidic), then adding a bunch of HCl whould also raise the pH, and I'm
pretty sure it doesn't.

I'll be interested to hear what others think, but I'm going with what I
said earlier:  the reason that CO2 lowers the pH of a wine solution is
that it increases the volume of the solution more than it increases
the absolute number of hydrogen ions.

But I could well be wrong.  This isn't the kind of chemistry I do, and
it's been 16 years since I've done this sort.

Dave
****************************************************************************

 
 
 

Ph & TA for merlot 2nd run

Post by David C Breed » Thu, 12 Oct 2000 04:00:00



Quote:

>>I'm no chemist, but maybe this answer (guess) makes intuitive sense:
>>Example:  A wine with no CO2 has a pH = 3.4.  You now introduce CO2 with a pH
>>of 6.8.  Blending should raise your pH 3.4 wine to something higher due to the
>>higher pH of CO2.  That seems why the CO2 could raise your pH instead of lower
>>it, even though it is an acid (although barely).
>>Make sense to others?
>Hi,
>That's intuitively appealing, but I don't think it can be right.  To
>raise the pH of a solution, you must do one of two things:  either
>lower the number of hydrogen ions in solution, or increase the volume
>of solution while keeping the number of hydrogen ions the same.
>If you keep the volume of a solution the same but add acid, you have
>to decrease the pH.  It could be I suppose, but I don't think it is,
>that addition of CO2 lowers the hydrogen ion concentration by shifting
>the pKa's of the other acids and making them less acidic.  But if that
>were true (if adding acids caused acids already in solution to be less
>acidic), then adding a bunch of HCl whould also raise the pH, and I'm
>pretty sure it doesn't.
>I'll be interested to hear what others think, but I'm going with what I
>said earlier:  the reason that CO2 lowers the pH of a wine solution is
>that it increases the volume of the solution more than it increases
>the absolute number of hydrogen ions.
>But I could well be wrong.  This isn't the kind of chemistry I do, and
>it's been 16 years since I've done this sort.
>Dave

Correction:  "lowrs the pH" above should "rasies the pH".  Sorry.

Dave
****************************************************************************

 
 
 

Ph & TA for merlot 2nd run

Post by Greg Coo » Thu, 12 Oct 2000 04:00:00


I am a chemist and this is almost correct.  Keep in mind that what we
call an acid or a base is relative.  A pH 3.4 solution is quite acidic.
CO2 is acting like a base by reacting with free H+ (and OH from water)
to form carbonic acid (CO3H2).  The pH of carbonic acid is higher 6.8.
pH refers to the equilibrium reaction, HA + H2O --> A- + H3O+ (or H+ if
you will).  HA being the acid - in this case a mix of acids.  When you
introduce the "base" CO2, you change this equilibrium, thus changing
the H+ concentration.

So in a sense, you are on track.


Quote:


> >I'm no chemist, but maybe this answer (guess) makes intuitive sense:

> >Example:  A wine with no CO2 has a pH = 3.4.  You now introduce CO2 with a pH
> >of 6.8.  Blending should raise your pH 3.4 wine to something higher due to
> >the
> >higher pH of CO2.  That seems why the CO2 could raise your pH instead of
> >lower
> >it, even though it is an acid (although barely).

> >Make sense to others?

> Hi,

> That's intuitively appealing, but I don't think it can be right.  To
> raise the pH of a solution, you must do one of two things:  either
> lower the number of hydrogen ions in solution, or increase the volume
> of solution while keeping the number of hydrogen ions the same.

> If you keep the volume of a solution the same but add acid, you have
> to decrease the pH.  It could be I suppose, but I don't think it is,
> that addition of CO2 lowers the hydrogen ion concentration by shifting
> the pKa's of the other acids and making them less acidic.  But if that
> were true (if adding acids caused acids already in solution to be less
> acidic), then adding a bunch of HCl whould also raise the pH, and I'm
> pretty sure it doesn't.

> I'll be interested to hear what others think, but I'm going with what I
> said earlier:  the reason that CO2 lowers the pH of a wine solution is
> that it increases the volume of the solution more than it increases
> the absolute number of hydrogen ions.

> But I could well be wrong.  This isn't the kind of chemistry I do, and
> it's been 16 years since I've done this sort.

> Dave
> ****************************************************************************


 
 
 

Ph & TA for merlot 2nd run

Post by David C Breed » Fri, 13 Oct 2000 04:00:00


Quote:

>I am a chemist and this is almost correct.  Keep in mind that what we
>call an acid or a base is relative.  A pH 3.4 solution is quite acidic.
>CO2 is acting like a base by reacting with free H+ (and OH from water)
>to form carbonic acid (CO3H2).  The pH of carbonic acid is higher 6.8.
>pH refers to the equilibrium reaction, HA + H2O --> A- + H3O+ (or H+ if
>you will).  HA being the acid - in this case a mix of acids.  When you
>introduce the "base" CO2, you change this equilibrium, thus changing
>the H+ concentration.
>So in a sense, you are on track.

Hmm.  Thanks!

In your explanation above, when the CO2 reacts with free H+ and OH
from water, doesn't it necessarily generate another free H+ from
water, thereby making the whole reaction a tossup from the pH point of
view?  That's what I had thought.

Dave
****************************************************************************