Testing TA

[yakhunter]

Hi everyone!

Our Zinfandel grapes FINALLY got here on Thursday! Two weeks later than my Syrah, so I was expecting a monster as the Syrah was 28.5 Brix (1.120 SG) at 64F and 4.1-4.2 pH.

The Zin was closer to normal. 1.110 and pH 3.8. I tried to test the TA with my pH meter for the first time and I am hoping one of you chemistry-types might feel like checking my work and seeing if I did it right.

1. Put 5 ml must in a small shot glass and added water to get depth that would work with probe-less pH meter.
2. Added 3 drops phenolphthalein
3. Initial pH was 3.8; shooting for 8.2 according to Morewine’s instructions)
a. After adding 2.5ml NAOH, it rose to 5.5
b. Added another 0.5 ml=>6.3
c. Added another 0.5 ml => 7.2
d. Added another 0.3 ml =>7.8
e. Added another 0.2 ml => 8.4; D’OH!!
f. So I overshot the 8.2 mark and interpolated a reading of 8.2 if I had not added that last 0.1 ml. This Kentucky windage approach earned me very average grades in 3-4 years of chemistry between high school and college, but its all I’ve got.
4. I added a total of 4.0ml, so figured the 8.2 pH mark was closer to 3.9 ml. Multiplying that by 1.5 as per instructions, I get a TA of 5.85 g/l. A little low, but easily correctible.
5. Did I do this correctly, and can I go ahead and pitch the yeast and correct acidity afterwards?
6. SG is 1.110 @ 64 F

Thanks in advance!

 

[ibglowin]

Are you using a Morewine TA kit? Sounds like it. If you are and or you are using 0.1N NaOH then your math is correct. I would rerun and go slow as you get to pH 7, drop, swirl, drop, swirl...... Sneek up on pH 8.2. Also, you don't need the phenolphthalein if your using the pH meter, thats only needed if your using your eye to detect the endpoint.

 

[ibglowin]

Forgot to mention that yes, sounds like your Zin needs some Tartaric Acid as well as your Syrah. You may also want to add some acidulated water to the Syrah to drop the brix down a bit. That would make a nearly 17% ABV wine if left alone!

 

[GreginND]

If you are using 0.1N NaOH, then your calculations are spot on. By the way, the tiniest amount will overshoot the pH so I wouldn't sweat it that much. 5.85 vs 6 is probably within experimental error anyway. It's not a bad TA and seems to consistent with your pH as much as they can be consistent. How does it taste? You could add a little acid but I wouldn't adjust it too much. Maybe 1 g/L if you want to try to lower the pH.

 

[RegionRat]

Something is very wrong! I actually understood what you guys are talking about......

RR

 

[shoebiedoo]

LOL. ME TOO!

I'm afraid!

 

[SBWs]

Only problem I see is step 1, did you add tap water or distilled water? You only say water. If distilled then I'd say you are okay, if it was tap water I don't know if it would be right.

 

[yakhunter]

Thanks everyone!

I used tap water, but we are on a well and it is high quality. Of course I suppose I do not know the pH...
I did add water and Tartaric acid to the Syrah pre-ferment to bring it down to 1.115 SG and an appropriate pH/TA
The Zin came from the same Vineyard as the Syrah, and was on the vines for over 2 extra weeks, yet had more acid and less sugar and was just generally less ripe. Is this a difference in the varietals or more likely microclimate?

 

[ibglowin]

Could be a bit of both.