TA calculation help

[Jim Welch]

I picked up 2 Chilean juice buckets yesterday (1 Zinfandel and 1 Merlot) and pulled samples to check brix, ph, and TA. I bought a testing kit when I picked up the buckets and used a ph meter because of a red/green defect so my fine color vision is not to be trusted. This is the first time I've checked the TA as up to now I've only made grape wine with kits. From the results I'm getting I think I'm making a mistake. Here is what I came up with, any help would be appreciated.

For the Zinfandel the Brix is 21.7 and the ph is 3.51. Using my ph meter and a stir plate I used Sodium Hydroxide with a Normality of 0.2 and a total wine sample size of 30 mL. It took ~4.5 mL to raise the samples ph to 8.20

For the Merlot the Brix is 20.2 and the ph is 3.48. Using my ph meter and a stir plate I used Sodium Hydroxide with a Normality of 0.2 and a total wine sample size of 20 mL. It also took ~4.5 mL to raise the samples ph to 8.20

Searching here I found this post from 2017 in a discussion on TA testing.

This is the generic formula for using any sample size and any strength NaOH

TA as tartaric acid in (g/100 ml (or %)) = (V)(N)(75)(100)/(1000)(v)

V = ml of sodium hydroxide solution used for titration
N = Normality of sodium hydroxide solution
v = sample volume (ml)

So plugging my values in I get a TA of 0.225 for the Zin and 0.3375 for the Merlot and these results seem very very low but this is the first time I've done this.

I did calibrate the ph meter before taking the ph readings using calibration buffers of 6.86 and 4.01 then immediately ran the TA test. Not sure if I should have recalibrated before the TA test using the 6.86 and a 10 ph buffer?

Also I'll mention this and not sure if it affected the test but I did the Zinfandel TA test first starting with a 25 mL sample and while adding the Sod. Hydr. squeezed the plunger a bit too hard and shot past 8.20 to around 8.60ish and added 5 mL more juice which brought the sample ph down to around 7.80ish then I continued the test taking more care to add a drop at a time until I reached a ph of 8.20.

Thanks for reading.

 

[toadie]

I'm new to testing for TA (started last year). I use .2 mol naOH as well.

TA= 75(ml of NaOH)(.2mol) / 15 ml sample of wine

75 (.2) =15 so essentially I add the ml of NaOH in my 10 ml syringe and once the ph is at 8.2 the amount of NaOH added is the TA.

I hope I've explained it clearly enough. I look forward to gentle corrections and admonishments for small sample size.
My goal is approximate TA especially considering my current Hanna pH meter only goes to one decimal.
Cheers!

 

[cmason1957]

This is the procedure and manual I used back when I actively tested TA. Pretty much nowadays, I check the PH and if it is in a range I find acceptable (3.4-3.7) and the taste is pretty good, I don't measure the TA. I found that I generally made things not better in the end by messing with it. For red wines, I try to get the PH as close to 3.6 as I can, with a fairly acceptable taste (not sharp, not flat) and call it good. This file came from Fisher Scientific, so I found it somewhat useful.

 

[Jim Welch]

This is the procedure and manual I used back when I actively tested TA. Pretty much nowadays, I check the PH and if it is in a range I find acceptable (3.4-3.7) and the taste is pretty good, I don't measure the TA. I found that I generally made things not better in the end by messing with it. For red wines, I try to get the PH as close to 3.6 as I can, with a fairly acceptable taste (not sharp, not flat) and call it good. This file came from Fisher Scientific, so I found it somewhat useful.

Thank you for the link, I’ll take look at it later when I can get on a computer. Those TA numbers I come up with seem very low compared to what I’ve read of but again I’ve no experience doing this testing.
If you had these pails with the ph of 3.48 and 3.51 would you leave well enough alone and go with it? Or would you try to get it closer to 3.60. I do plan to do a malolactic fermentation on these pails if that makes a difference which will be another first for me. The balance of the samples I pulled, the portion not tested tasted great as far as I could tell. Wine juice always seems much much better than “regular” grape juice, very rich and flavorful.

 

[BarrelMonkey]

Is that brix/pH typical for chilean zin/merlotgrapes? I would normally expect higher brix for that pH level. Assuming you're confident in your pH measurement, I would probably leave it as is (though my experience is with pinot noir rather than zin/merlot).

 

[Jim Welch]

I am confident in the ph, it is a fairly new probe and I calibrated it immediately beforehand. I agree the Brix does seem low, I’ve only made kits so far but about half dozen of each type and typical in my limited experience is close to 25 Brix for the Zin and slightly lower for Merlot. The Merlot had started fermenting, bucket lid was slightly domed and the Zin lid was slightly concave. The Merlot had foam escape as I opened it but not so for the Zin. I wouldn’t be surprised if the Zin had fermented a tiny bit too but not nearly as active as the Merlot. I gave both buckets a fairly heavy dose meta k, stirred and put them in my spare fridge. Waiting for my grape lugs to arrive this week to put the wine must together and start it.

 

[cmason1957]

Given that it has started fermenting, I would let it go and decide on adjustments after fermentation is complete. I might not do MLF on these, but I might. Not sure how I would make the decision on that. Conventional wisdom says always do it, so it doesn't happen later.

 

[Rice_Guy]

The numbers are possible. The club had nine pallets of Chilean juice last week. With this year the sugar was typically 1.087. PH on whites typical 3.1 and reds typical 3.4. TA typical was 0.3% to 0.5%.
PM me if you want to see the QA data set.

 

[sour_grapes]

The numbers are possible. The club had nine pallets of Chilean juice last week. With this year the sugar was typically 1.087. PH on whites typical 3.1 and reds typical 3.4. TA typical was 0.4% to 0.5%.
PM me if you want to see the QA data set.View attachment 88174

Note that in rice guy's post, the containers are depicted upside down because they are from Chile.