Malolactic conversion will typically reduce acidity. Malic acid, a
dicarboxylic acid, gets decarboxylated to form lactic acid, a
monocarboxylic acid, and CO2(g). This will likely raise the pH
(though not dramically in my hands), not lower it.

Malate, like residual sugar, is a potential energy source for
bacteria. One goal of ML'ing is to remove that potential energy
source. Many species of lactic acid bacteria may be present in a
wine. Some are benign, some are considered spoilage bacteria. Any of
them may eventually utilize the malate under the right conditions
(temp above 65F, pH above 3.2, low sulfite levels, sufficient
nutrients, etc.). It can and does occur after bottling, which can be
heartbreaking after all your effort, leaving you with spoiled wine.
Encouraging the ML conversion by innoculating with a benign strain (O.
oenos) helps me sleep a bit better at night.

To ML or not is entirely up to you. Be sure to maintain adequate SO2
levels for your wine's pH if you choose not to ML.

RD

This is an excellent thread!! I'd like to skew off on a related but
tangent subject if you guys will humor me for a moment...

I recently attended a seminar in which one of the topics was
winemaking techniques for Cynthiana/Norton grapes. These grapes are
typically very high in acid (1.2) and often high pH (3.5). The
presenter was advocating the addition of tartaric acid to drop the pH
down to 3.5 prior to fermentation and let the acid fall where it may.
Then cold stabilize after fermentation to precipitate out tartrates
and get the acidity back down. Here's my rub(s):

1. Some resources claim that ML is inhibited in musts with acidity
greater than 1.0. By adding tartaric, the must acidity will exceed
1.2! If these resources are correct, wouldn't the odds of ML inception
and completion be slim? They say ML is particularly important in wine
musts high in malic acid like Cynthiana. What gives?

2. If resources mentioned in #1 above are right, wouldn't acidity in a
pre-fermented wine must be more important than pH to ensure successful
ML? I know pH is very important for long-term stability of wine after
bottling but does it really matter during vinification? Can't wine
stability issues from high pH levels be dealt with after fermentation
simply by adding a little more SO2 prior to bottling?

3. Once the cold stabilization precipitates out the tartaric acid,
wouldn't the must acidity and consequently pH end up right about where
it started before the tartaric addition? If yes, what was the point?

Please enlighted me. I sense I've been missing something crucial in my
winemaking process!

Concerned,
Charles Erwin



On Sat, 15 Sep 2007 18:15:13 -0700, RD
wrote:

I would approach this the other way around. Add tartaric acid to
bring pH into the 3.5 range then check the TA. pH is much more
important from a microbial stability standpoint, than TA. Excess
tartaric acid can be dropped out when cold stabilizing. The potential
problems of a high pH environment are less easily remedied.

I would not skip the ML on your Zin, again, more for stability than
style. Consider lysozyme if you decide not to ML your Chard.

RD

I've included my understanding of your points within your message.

I hope I'm not being too technical to be understood.

Gene

Charles E wrote:
This is an excellent thread!! I'd like to skew off on a related but
tangent subject if you guys will humor me for a moment...

I recently attended a seminar in which one of the topics was
winemaking techniques for Cynthiana/Norton grapes. These grapes are
typically very high in acid (1.2) and often high pH (3.5). The
presenter was advocating the addition of tartaric acid to drop the pH
down to 3.5 prior to fermentation and let the acid fall where it may.
Then cold stabilize after fermentation to precipitate out tartrates
and get the acidity back down. Here's my rub(s):

1. Some resources claim that ML is inhibited in musts with acidity
greater than 1.0. By adding tartaric, the must acidity will exceed
1.2! If these resources are correct, wouldn't the odds of ML inception
and completion be slim? They say ML is particularly important in wine
musts high in malic acid like Cynthiana. What gives?

I've not heard before about acidity greater than 1.0 inhibits MLF. One
commercial winery I know of occasionally adds 1 gm/liter tartaric acid
without inhibiting MLF. Can you provide a reference that I might read
in which this claim is made?

MLF is inhibited when the pH is lower than 3.1. Adjusting pH downward
to 3.5 is not enough to inhibit ML fermenation.

MLF is inhibited by small additions of fumaric acid, but we don't adjust
pH in our grape must with fumaric acid.

2. If resources mentioned in #1 above are right, wouldn't acidity in a
pre-fermented wine must be more important than pH to ensure successful
ML? I know pH is very important for long-term stability of wine after
bottling but does it really matter during vinification? Can't wine
stability issues from high pH levels be dealt with after fermentation
simply by adding a little more SO2 prior to bottling?

The yeast's ability for vinification of grapes is not noticeably
affected even at high grape pH. High grape pH does allow some kinds of
bacteria to grow during vinification which can cause off-flavors, so you
have pay more attention to sanitation practices when fermenting high pH
grapes.

At pH greater than 3.8, the chemical form of sulfur which protects the
wine (called molecular sulfur) is in such low concentration that
oxidation and bacterial spoilage of the wine are real risks, unless so
much SO2 is added that you begin to taste it in the wine.

Oxidation and bacterial spoilage is more a problem for white wines than
red wines because the polyphenol compounds in the red wines do offer
some protection.


3. Once the cold stabilization precipitates out the tartaric acid,
wouldn't the must acidity and consequently pH end up right about where
it started before the tartaric addition? If yes, what was the point?

Potassium ions in the grapes are largely responsible for the high pH.
When you lower pH using tartaric acid additions, the tartaric acid
reacts with potassium ions to form potassium bitartrate. Cold
stabilization precipitates (forms crystals) of potassium bitartrate
which do not redissolve in the wine at normal wine storage temperatures.
With the fraction of potassium ions gone from the wine, the pH will stay
lower than where it started.

Other chemical reactions in the wine can raise the pH again, but usually
less than the amount we have lowered it by removing the potassium ions.



Please enlighted me. I sense I've been missing something crucial in my
winemaking process!

Concerned,
Charles Erwin



On Sat, 15 Sep 2007 18:15:13 -0700, RD
wrote:

I would approach this the other way around. Add tartaric acid to
bring pH into the 3.5 range then check the TA. pH is much more
important from a microbial stability standpoint, than TA. Excess
tartaric acid can be dropped out when cold stabilizing. The potential
problems of a high pH environment are less easily remedied.

I would not skip the ML on your Zin, again, more for stability than
style. Consider lysozyme if you decide not to ML your Chard.

RD

Charles,
I've not heard anything about high TA being an issue with ML either
but most of the books I read don't talk a lot about hybrid
winemaking. I have a few that do so I'll look. I'm hoping to make a
few hybrids this year and it's always good to brush up. I'm sure the
people at Cornell have thoughts on this and most of their work is not
to hard to find on the internet. An email to them always gets
answered also.

Did the mention using Lalvin 71B? It likes malic acid and often
consumes a bit of it during fermentation.

RD,
I probably could have phrased that previous post better; I was not
saying ML will lower pH. I was saying shooting for a pH of 3.5 might
not add enough tartaric to bring the potassium out. It's my
understanding that high TA and high pH usually indicates a high
potassium level. Genes post was much clearer on that. Tom S always
shoots for 3.3 as I remember it.

Joe

Hi Joe, Thanks for the clarification. I see what you meant now about
high TA/ high pH/ and K+.

RD

They are about done fermenting
I have racked the Chardonnay because it had a slight sulfur smell.
I will press the Zin shortly

My new numbers.

Chardonnay
SG 0.995
pH 3.45
TA 0.68


Zinfandel
SG 1.005
pH 3.6
TA 0.77

I added ML and nutrient to the Zin today

Thanks for clearing this up for me Gene, Joe, and RD. The resource I
was referring to was Home Winemaking by Iverson. After reading your
responses, I reconsulted the book and found I took a statement out of
context about high acid and ML and missing the real point of the
chapter on raising acidity. After more careful reading, Iverson is
consistent with your comments. How could I have missed such a
fundamental and critical point!?! That does explain why one of my high
pH wines I made in the past ended up with slight off aromas even
though I was careful to keep the SO2 levels consistent with the chart
recommendations AFTER fermentation.

Thanks again for your advice guys! It is much appreciated by this
novice winemaker...

Charles


On Thu, 20 Sep 2007 13:27:17 GMT, gene wrote:

I've included my understanding of your points within your message.

I hope I'm not being too technical to be understood.

Gene

Charles E wrote:
This is an excellent thread!! I'd like to skew off on a related but
tangent subject if you guys will humor me for a moment...

I recently attended a seminar in which one of the topics was
winemaking techniques for Cynthiana/Norton grapes. These grapes are
typically very high in acid (1.2) and often high pH (3.5). The
presenter was advocating the addition of tartaric acid to drop the pH
down to 3.5 prior to fermentation and let the acid fall where it may.
Then cold stabilize after fermentation to precipitate out tartrates
and get the acidity back down. Here's my rub(s):

1. Some resources claim that ML is inhibited in musts with acidity
greater than 1.0. By adding tartaric, the must acidity will exceed
1.2! If these resources are correct, wouldn't the odds of ML inception
and completion be slim? They say ML is particularly important in wine
musts high in malic acid like Cynthiana. What gives?

I've not heard before about acidity greater than 1.0 inhibits MLF. One
commercial winery I know of occasionally adds 1 gm/liter tartaric acid
without inhibiting MLF. Can you provide a reference that I might read
in which this claim is made?

MLF is inhibited when the pH is lower than 3.1. Adjusting pH downward
to 3.5 is not enough to inhibit ML fermenation.

MLF is inhibited by small additions of fumaric acid, but we don't adjust
pH in our grape must with fumaric acid.

2. If resources mentioned in #1 above are right, wouldn't acidity in a
pre-fermented wine must be more important than pH to ensure successful
ML? I know pH is very important for long-term stability of wine after
bottling but does it really matter during vinification? Can't wine
stability issues from high pH levels be dealt with after fermentation
simply by adding a little more SO2 prior to bottling?

The yeast's ability for vinification of grapes is not noticeably
affected even at high grape pH. High grape pH does allow some kinds of
bacteria to grow during vinification which can cause off-flavors, so you
have pay more attention to sanitation practices when fermenting high pH
grapes.

At pH greater than 3.8, the chemical form of sulfur which protects the
wine (called molecular sulfur) is in such low concentration that
oxidation and bacterial spoilage of the wine are real risks, unless so
much SO2 is added that you begin to taste it in the wine.

Oxidation and bacterial spoilage is more a problem for white wines than
red wines because the polyphenol compounds in the red wines do offer
some protection.


3. Once the cold stabilization precipitates out the tartaric acid,
wouldn't the must acidity and consequently pH end up right about where
it started before the tartaric addition? If yes, what was the point?

Potassium ions in the grapes are largely responsible for the high pH.
When you lower pH using tartaric acid additions, the tartaric acid
reacts with potassium ions to form potassium bitartrate. Cold
stabilization precipitates (forms crystals) of potassium bitartrate
which do not redissolve in the wine at normal wine storage temperatures.
With the fraction of potassium ions gone from the wine, the pH will stay
lower than where it started.

Other chemical reactions in the wine can raise the pH again, but usually
less than the amount we have lowered it by removing the potassium ions.



Please enlighted me. I sense I've been missing something crucial in my
winemaking process!

Concerned,
Charles Erwin