Driving me crazy.

[DaveLap]

Acid level at start of fermentation was .88 tartaric. Now, four weeks later with fermentation winding dow, the acid level is 1.125! How is this possible? And it happens every year and with multiple reruns on the test to verify?

 

[CoteRotie]

Hmm.. Are you making wine from frozen must?

 

[DaveLap]

Hmm.. Are you making wine from frozen must?

No, making it from juice.

 

[stickman]

Make sure the sample is degassed before running a TA test; warm sample and shake to degas, cool back to room temp before testing. A sample saturated with CO2 can test 2 to 3g/l higher than actual.

 

[salcoco]

fermentation generate carbonic acids, useless to measure while fermenting wait until wine is clear and degassed before making measurements. at least three months post fermentation

 

[DaveLap]

I degassed the sample by 20 second microwave and allowed to cool back to room temperature. I can test acidity periodically but would like to adjust if necessary at first racking. Right now the sugar is <100 and the lees are piling up. What do you guys think?

 

[Rice_Guy]

I also microwave, ,, 100 ml for 55 sec
yes CO2 makes carbonic acid and I have seen the yeast force the pH down to 2.8

I degassed the sample by 20 second microwave and allowed to cool back to room temperature. I can test acidity periodically but would like to adjust if necessary at first racking. Right now the sugar is <100 and the lees are piling up. What do you guys think?

* the purpose of acid in the primary is to regulate chemical reactions and microbial infections. In general lower is better however yeast really don’t like under pH 3, this means TA doesn’t matter in the primary but pH does, ,,, however broadly speaking they follow each other.
* the purpose for TA is to give a refreshing flavor when bottled, you could wait to “fix” TA as long as pH was correct.

 

[DaveLap]

Thanks everyone!
I will have to get myself a pH test kit and start watching this value as well. I can put off racking for a while. I'll see what happens. By the way, does anyone know if there is a "standard" acid solution against which I can check my testing kit/technique? Shouldn't take that off the table as a potential issue though I'm fairly confident that I am correctly identifying the end point.

 

[cmason1957]

Since you say you need to get a Ph meter (test kit), I am guessing you are trying to use the color change to determine when to stop the titration in determining the TA value. Nice thing about having that ph meter is you don't have to care about the color change any longer. It happens at a PH of 8.2 so you titrate to that value not some arbitrary color point.

 

[Rice_Guy]

as Craig says a pH meter, even a very cheap one will do the job.
The standard acid in chemical methods is succinic acid, ,,,, it is fairly high weight per mole so reasonably accurate with an analytical balance. no it isn’t worth your effort.

I would argue that you are a home wine maker, your standard error with a home TA kit was 0.02 to 0.04%, ,,, not a lot when calibrating against a taste panel but a lot if your end goal is 0.60% TA. ,,, basically I know more folks in the wine club who don’t measure much beyond gravity and as much as I encourage, they don’t do anything to “fix” TA. ,,, your OP concern is high TA, the real question should be how does it taste when finished? ex I have seen a cranberry wine with 2.0% TA which was a great flavor (we expect cranberry to be sharp). Frequently a high TA wine can be balanced by adding sugar.

Thanks everyone!
I will have to get myself a pH test kit and start watching this value as well. I can put off racking for a while. I'll see what happens. By the way, does anyone know if there is a "standard" acid solution against which I can check my testing kit/technique? Shouldn't take that off the table as a potential issue though I'm fairly confident that I am correctly identifying the end point.

 

[DaveLap]

as Craig says a pH meter, even a very cheap one will do the job.
The standard acid in chemical methods is succinic acid, ,,,, it is fairly high weight per mole so reasonably accurate with an analytical balance. no it isn’t worth your effort.

I would argue that you are a home wine maker, your standard error with a home TA kit was 0.02 to 0.04%, ,,, not a lot when calibrating against a taste panel but a lot if your end goal is 0.60% TA. ,,, basically I know more folks in the wine club who don’t measure much beyond gravity and as much as I encourage, they don’t do anything to “fix” TA. ,,, your OP concern is high TA, the real question should be how does it taste when finished? ex I have seen a cranberry wine with 2.0% TA which was a great flavor (we expect cranberry to be sharp). Frequently a high TA wine can be balanced by adding sugar.

Typically, my finished product is somewhat heavy and more astringent then I desire. I prefer a lighter, dryer wine with a slight sweetness/fruitiness. I don't seem to be able to get that and I suspect that the acid is the culprit. Could I be wrong here? Anyway, my acid test kit uses only a small aliquot (3ml) so testing the pH on that small of a sample would be problematic. Anyone know a better method for using pH to determine endpoint?

 

[Rice_Guy]

FROM A LAB BENCH POINT OF VIEW:
slightly sweet correlates with low acid to get balance
fruity and fruity aroma correlates with more sugar
astringent can correlate with oxidized alcohol (depends on how well panel names flavors)
astringent correlates with stems and crushed seeds with grape and always accompanies aronia berry or alum (a good reference when training a panel)
astringent balances with sugar, ,,, ie more of one is more of both
bitter correlates with tannin (ex steeped red grape skins/ longer lasting flavor notes) and potassium (ex light salt)
bitter balances with more sugar and usually less acid
burn in the back of the throat correlates with oxidized alcohol (AKA acetaldehyde)

Part of me wonders how your product compares with commercial product with the same ingredient? ,,, HEAVINESS Is not a term that I have been using with wine, I usually give high fat sauces that descriptor.

I have an Extech (flat bulb) pH meter so occasionally measure one drop 0.1 ml, ,,, when doing TA with a pH meter in stead of phenothalene indicator, you still stop at pH 8.2, and tend to get a sharper end point (not is it pink enough) and have continuous pH readings starting at the raw juice

Most grape folks who want to drop the TA do MLF, some folks who want to drop TA with cranberry add potassium bicarbonate or calcium carbonate. Will a few grains of potassium bicarbonate fix the flavor you are working on?

as always it would be nice to walk down the hall and taste/ give an opinion, ,,, pre COVID the local vinters club also gave neat feedback.

 

[DaveLap]

FROM A LAB BENCH POINT OF VIEW:
slightly sweet correlates with low acid to get balance
fruity and fruity aroma correlates with more sugar
astringent can correlate with oxidized alcohol (depends on how well panel names flavors)
astringent correlates with stems and crushed seeds with grape and always accompanies aronia berry or alum (a good reference when training a panel)
astringent balances with sugar, ,,, ie more of one is more of both
bitter correlates with tannin (ex steeped red grape skins/ longer lasting flavor notes) and potassium (ex light salt)
bitter balances with more sugar and usually less acid
burn in the back of the throat correlates with oxidized alcohol (AKA acetaldehyde)

Part of me wonders how your product compares with commercial product with the same ingredient? ,,, HEAVINESS Is not a term that I have been using with wine, I usually give high fat sauces that descriptor.

I have an Extech (flat bulb) pH meter so occasionally measure one drop 0.1 ml, ,,, when doing TA with a pH meter in stead of phenothalene indicator, you still stop at pH 8.2, and tend to get a sharper end point (not is it pink enough) and have continuous pH readings starting at the raw juice

Most grape folks who want to drop the TA do MLF, some folks who want to drop TA with cranberry add potassium bicarbonate or calcium carbonate. Will a few grains of potassium bicarbonate fix the flavor you are working on?

as always it would be nice to walk down the hall and taste/ give an opinion, ,,, pre COVID the local vinters club also gave neat feedback.

Thanks for the reply. Pardon my misuse of terms here. I guess that I am saying that my wine is the opposite of a light wine which is probably an incorrect term as well. Just a beginner here. Anyway, if I stick with .1N Sodium Hydroxide, then, according to my acidity kit, my 3 ml sample would be in a test tube and I would find it impossible to use the pH meter for endpoint. So, I'm assuming a much larger sample(better) would be in order so that I could titrate the NaOH and read the pH meter simultaneously. My question is whether the stoichiometry here is linear with respect to the higher sample volume. So if I went to say a 30 ml sample would I divide my mls of .1N NaOH by 10 before applying any multiplier? My gut tells me to upgrade to 1N NaOH but I'm not so sure of the safety ramifications as it would seem to be pretty strong stuff. Thoughts?

 

[stickman]

There's nothing wrong with .1N NaOH, most procedures direct you to add distilled or deionized water to increase sample size.

Sample Preparation
Make sure the wine sample is at room temperature. To minimize interference from CO2, degas an amount of the wine sample, e.g. 25 mL. Degas in a flask under vacuum for several minutes with agitation. Alternately, place a sample in an ultrasonic bath for a few minutes, bubble compressed air through to release excess CO2, or heat a sample to almost boiling, agitate, and let cool.
Sample Titration
Pipette 5.0 mL of degassed wine sample into a 150 mL beaker containing 50 mL DI. Immerse the electrode and stirrer in the solution. Turn on the stirrer.
Titrate with the NaOH titrant at a faster rate in the beginning and a slower rate when the pH reaches 6.5. It is not necessary to wait for a stabilized reading before pH 6.5. Then, start to add titrant slowly until the pH just exceeds 8.2. This is the endpoint of the titration. Record the volume of titrant used (Vs). Calculate the TA in g/L tartaric acid in the wine sample using the equation below. After each titration, rinse the pH electrode and stirrer with DI and tap to remove excess water droplets.

TA in sample:
TA (g tartaric acid/L) = (N NaOH) x (mLs NaOH) x 75)/mLs of sample

 

[Ignoble Grape]

Typically, my finished product is somewhat heavy and more astringent then I desire. I prefer a lighter, dryer wine with a slight sweetness/fruitiness. I don't seem to be able to get that and I suspect that the acid is the culprit. Could I be wrong here? Anyway, my acid test kit uses only a small aliquot (3ml) so testing the pH on that small of a sample would be problematic. Anyone know a better method for using pH to determine endpoint?

Really enjoying this thread - thanks to everyone who's contributing - excellent review for my enology final coming up next week @stickman I just had to do this lab yesterday. Going to be investing in a burret with a stopcock and .1N NaOH solution... Luv me some kitchen chemistry!

We don't know what kind of wine @DaveLap is making - We're talking acid here, but astringency can also be tannin. Some are naturally more astringent (tannic) than others - nebbiolos and cabs being the famous two. Eggwhites will bind with tannins and drop them out of the wine, making it less astringent. Lower alcohol will also give the wine a lighter mouthfeel. Good luck!

 

[JohnT]

One other simple thought is that you need to do a fine straining on your first test. I have found that particulate matter will throw off my TA test. For a PH test this is not as much of a concern. A lot of particulate matter settles out of the wine after fermentation giving a more "pure" sample, thus a higher TA reading.