I've always tried to correct any acid imbalances as soon as the grapes were
crushed, before beginning the primary fermentation. But lately, I've been
getting peculiar results, and I wonder if I should wait until the Brix is much
lower.

I had a blend of syrah and grenache which tested with a TA of .45 and a pH of
about 3.7 just after crush. I added a reasonable amount of tartaric which
should have brought the TA up to about .55-.60. After fermentation was
complete, though, I find a TA of .78 and a pH of about 3.18. I get the feeling
that there's a lot of acidity in the grape skins that might not be apparent
when I'm testing the juice just after crush.

Does this make sense? How do people get around these discrepancies? All of
the tests that I do are on well calibrated equipment and the tests are run
multiple times.

Lee

"LG1111" wrote:

I've always tried to correct any acid imbalances as soon as the grapes
were
crushed, before beginning the primary fermentation. But lately, I've been
getting peculiar results, and I wonder if I should wait until the Brix is
much
lower.

I had a blend of syrah and grenache which tested with a TA of .45 and a pH
of
about 3.7 just after crush. I added a reasonable amount of tartaric which
should have brought the TA up to about .55-.60. After fermentation was
complete, though, I find a TA of .78 and a pH of about 3.18. I get the
feeling
that there's a lot of acidity in the grape skins that might not be
apparent
when I'm testing the juice just after crush.

Does this make sense? How do people get around these discrepancies? All
of
the tests that I do are on well calibrated equipment and the tests are run
multiple times.

Assuming that your measurements are accurate, you are probably
overestimating that liquid volume of your must. You need to subtract about
15-25 % from the apparent volume in the primary (the exact figure depends
upon the size and condition of your grapes).

One way to handle this is to add HALF the tartaric acid indicated, stir, and
retest the must. If you achieved half the adjustment you calculated, you can
safely add the same quantity. If there is a discrepancy, adjust the
additional amount you are adding accordingly.

One way to handle this is to add HALF the tartaric acid indicated, stir, and
retest the must. If you achieved half the adjustment you calculated, you can
safely add the same quantity. If there is a discrepancy, adjust the
additional amount you are adding accordingly.


That makes sense, but on a really simplistic basis, when you taste a fresh
grape, the juice tastes sweet and the skin tastes tart. That must mean that
when the juice and skins are fully fermented, the resultant must is more acidic
than the starting juice.

Lee

"LG1111" wrote:
That makes sense, but on a really simplistic basis, when you taste a fresh
grape, the juice tastes sweet and the skin tastes tart. That must mean
that
when the juice and skins are fully fermented, the resultant must is more
acidic
than the starting juice.

That also makes sense, but .... try the same test after 24 hours of
fermentation (or cold-soaking), and you will see that most (if not all) of
the tartness (but not tannin content) has been adsorbed by the liquid must.

"LG1111" wrote in message
...
One way to handle this is to add HALF the tartaric acid indicated, stir,
and
retest the must. If you achieved half the adjustment you calculated, you
can
safely add the same quantity. If there is a discrepancy, adjust the
additional amount you are adding accordingly.


That makes sense, but on a really simplistic basis, when you taste a fresh
grape, the juice tastes sweet and the skin tastes tart. That must mean
that
when the juice and skins are fully fermented, the resultant must is more
acidic
than the starting juice.

Sorry, but that's not right. The juice tastes sweet, but the skin tastes
_tannic_. When the fermentation starts to break down the skins the pH goes
_up_ because of the release of potassium therein.

At the end of fermentation, the wine may taste noticeably acidic, but that's
due to dissolved CO2. That goes away with either barrel aging or degassing,
and ML fermentation will further reduce the wine's acidity.

Tom S

Sorry, but that's not right. The juice tastes sweet, but the skin tastes
_tannic_. When the fermentation starts to break down the skins the pH goes
_up_ because of the release of potassium therein.

At the end of fermentation, the wine may taste noticeably acidic, but that's
due to dissolved CO2. That goes away with either barrel aging or degassing,
and ML fermentation will further reduce the wine's acidity.

Tom S






Tom, of all contributors to this newsgroup, your comments are always helpful
and accurate, and I wish you lived next door. But I'm still confounded why I
get such screwy discrepancies when I test a freshly crushed must versus when I
wait for 4-5 days of fermentation. I virtually always see lower pH's after 4-5
days, and the TA's are often higher. I'm getting to the point where I think my
acid corrections are hurting more than helping.

Lee

"LG1111" wrote in message
...
I'm still confounded why I
get such screwy discrepancies when I test a freshly crushed must versus
when I
wait for 4-5 days of fermentation. I virtually always see lower pH's
after 4-5
days, and the TA's are often higher. I'm getting to the point where I
think my
acid corrections are hurting more than helping.

If you failed to degas your sample taken during fermentation it may very
well read higher TA than initially. I'm not sure about the pH going down
for that reason though. Try bringing your samples just to the boiling point
to drive off the dissolved CO2 before you run your measurements and see if
that helps.

BTW, when doing an acid addition always try it on a small sample first and
_taste_ it as a sanity check.

Tom S

I virtually always see lower pH's after 4-5
days, and the TA's are often higher. I'm getting to the point where I think my
acid corrections are hurting more than helping.

Lee

Lee, are you saying that you see these type of changes even if you
don't make any acid corrections, or that the numbers you measure after
you make an acid adjustment are not what they should be 4-5 days
later?

If the latter then you have to think about what Negodki said about
over or under-estimating the amount of juice you have in your must.
Are you taking measurements right after your adjustments as well or
just 4-5 days later?

If the former, then something else is going on.

"Tom S" wrote in message . ..
"LG1111" wrote in message
...
I'm still confounded why I
get such screwy discrepancies when I test a freshly crushed must versus
when I
wait for 4-5 days of fermentation. I virtually always see lower pH's
after 4-5
days, and the TA's are often higher. I'm getting to the point where I
think my
acid corrections are hurting more than helping.

If you failed to degas your sample taken during fermentation it may very
well read higher TA than initially. I'm not sure about the pH going down
for that reason though. Try bringing your samples just to the boiling point
to drive off the dissolved CO2 before you run your measurements and see if
that helps.

BTW, when doing an acid addition always try it on a small sample first and
_taste_ it as a sanity check.

Tom S

Lee, as Tom says, at 4-5 days of fermentation your wine is going to be
high in dissolved CO2 which means carbonic acid in your wine which
will both raise TA and lower pH. So that's a very difficult time to
make reliable measurements of either. As Tom also says, if you want
to try to measure either TA or acid during or just after fermentation,
you need to take measures to degas your sample, by boiling and/or
shaking vigorously. Your apparently increased acidity may well have
something to do with dissolved CO2. All of the advice you've gotten
on taking care with additions is good, though - whether it's sugar,
SO2, acid, or anything else, putting it in is a lot easier than
getting it out ;^)

- Mark W.