first time winemaker adjusting TA

[fireguy94]

Hi Guys,

Ok so today was the big day. We went to pick up the grapes today and came back with 33 legs. We did 11 of cab sav, 11 of merlot and 11 of zin. We had them crushed and destemed at the store and then combined them into 3 large primary fermenters once we brought them home. First thing I did was check the sugar content with my refractometer. It read 23.6% brix. That works out to 12.3% alcohol. We were fine with that so we carried on. Now the problem came. Next we checked the TA. I did the TA test and it came up at 0.2. From what I read we need to be at 0.6-0.9 so we were well short. Obviously we need to make an adjustment with tartaric acid. I just want to check the dosage cause it seems like a lot! If I aim to increase by 0.5 to have a total TA of 0.7 I believe I need quite a bit of TA. I used the forumla 1g/L adjust TA 0.1%. I have 3 primaries that are filled to 165L each. Based on that forumla I need 825g of TA for each primary. Thats almost 3kg of TA!!!! That seems like a crazy amount. Can someone check and make sure I'm doing this correctly. I've dont the TA test twice now and came up with the same results both times.

Matt

 

[Flame145]

Describe your procedure for TA testing. Are u titrating w/ a ph meter ?

 

[ibglowin]

If these are California grapes I find it hard to believe that TA is correct. The weather has been text book perfect in every wine growing region of the State so acid readings should be much higher than that.

What is the pH of the must?

 

[GreginND]

I suspect you are calculating the TA for the wrong sample size or NaOH normality. Triple check your measurements and calculations.

 

[fireguy94]

Thanks for the replies guys. So my TA procedure is this. I took a sample of must and strained and used a coffee filter to get 15ml in a small beaker. I then add 4 drops of indicating solution. Then i drew out 10ml of hydroxide. The initial PH reading of the sample is 4.69. Using my PH meter i added 1 ml to the mix and stirred. It came up to 6.8. I added another ml and it came up to 8.5. My end point was supposed to be 8.2 so i stopped at 2 ml. The sample at this point had changed to a dark blue color. Based on 2 ml that is.0.2% TA From what im reading. My PH meter is new and I've used storage solution since i had it. I believe the calibration is correct. Maybe i should attempt to try the TA test without the meter.

Matt

 

[GreginND]

Your pH seems to be way out of range. I think you need to calibrate and check your meter again. I would also suggest you add the NaOH more slowly - drop wise - so you don't overshoot the pH. It helps also to dilute your wine sample with 50 mL or so of DI water.

 

[fireguy94]

Ok i calibrated my PH meter again. I used the 7.01 buffer solution. I did check on the must. My reading was 4.84. I re did the TA test and diluted the 15ml sample with 50ml of DI water. I got exactly the same results. If anything its just under 2ml. Im using 1/5n hydroxide solution if that makes a difference.

Matt

 

[ibglowin]

Something is terribly wrong with those grapes or your meter.

What type are they and where did they come from?

 

[fireguy94]

They are from California. Im using cab sav, merlot and zin. I live in Vancouver Canada and got them from an importer. He sells a lot of grapes every year. Well known in the area. Im new but does it have to do with the fact that the varieties we picked are not very acidic. If one of the grapes had been more acidic it would of balanced better. As for the PH Meter i believe its accurate. I've used it for brewing a couple times and had to make adjustments to my mash. The before and after readings were in line with the quantities i added to the mash. Even when i did the TA test without the PH meter i got the same results. Also to add the taste of the juice is very sweet with no tartness in it.

Matt

 

[GreginND]

Sorry, I don't mean to keep questioning your numbers but they really are very unusual if true.

Did you calibrate your pH meter with both 7.01 and 4.01 pH standards? You need to do that to establish the correct slope. Calibrating just on one pH only provides an accurate reading near that pH.

If your numbers are correct then I would say you should talk to your supplier and complain. Those grapes have a serious flaw.

I think your calculations look right on the amount of tartaric acid. To adjust, I would add no more than half the amount, stir well and recheck the numbers again. Add slowly so you don't overshoot your target.

 

[fireguy94]

I didn't calibrate it with both. I just have the 7.01 solution. I could go buy the 4.01 but its about an hour drive to get it. Would it really make that big of a difference.

 

[GreginND]

Generally if you haven't done a two point calibration for some time, a one point calibration may not be good. What do the instructions for your pH meter say about calibration?

Also, are you using 0.2N NaOH for your titration?

 

[fireguy94]

Well its a brand new hanna phep 5 atc meter. I got it about 2 weeks ago so it should already be calibrated. As for the solution im using 1/5n. Which i guess works out to 0.2. The instructions say if your using 1/10 you need to double the amount. Ie 2cc = 0.1% instead of 1cc. Im going to make an adjustment to 1 of the primaries and try and bring it up 0.1% and see if i get that reading. I start very small.

Matt

 

[fireguy94]

Ok so I've done the adjustment and based on what i got im very confident that its the grapes and not my readings. So i decided to try adjusting one batch 165L by 0.1%. So i dissolved 165g of tartaric acid into some warm water and mixed it into the batch. I stirred it very thoroughly and drew off a test sample. I strained this through a coffee filter and got 15ml of juice. I added 50ml of distilled water and 3 drops of indicating solution. I did the test and this time added 3 ml of hydroxide. That means i raised the acidity by 0.1% that as far as i can tell my testing is accurate. Let me know if you guys see any flaws in my test procedure. Also what's up with the grapes. From what you guys have said there way out of line. Will this make decent wine if i adjust the TA.

Matt

 

[ibglowin]

I would call the guy you bought them from and see if he has any numbers from anyone else who got the same grapes.

 

[fireguy94]

Ok i did some follow up. The grapes all came from lodi CA. They came from various vineyards ib the area. So with a quick Google search i got a number to a few vineyards in lodi and gave them a call. I told them my situation and she said that all the grapes in that area are coming in low on acid this year.

 

[ibglowin]

This is like the best growing season in a long long time. Grapes should be as perfect as they get. I have seen a pH of ~4.00 before with a TA ~ 4 g/l but I have never seen a ripe grape (Vinifera Noble) with that high a pH from CA. If you trust your pH meter then you can add acid to bring the acid of to about 7.5 g/l and get the pH down to around 3.6 or so. On the other hand you can just ferment them as is and add acid after you ferment to dry. This will buy you time to talk to others who bought those grapes and see if they have similar numbers.

 

[GreginND]

Wow. I am still amazed at those numbers but you are convincing me. I would try to adjust the acid now as that would be best. Maybe by .2 % at a time. How does the must taste?

As for the quality of the wine I think it's hard to say. With numbers that far off other chemistry in the grape could be whacked. But I don't think I would worry about it at this point. There's not much you can do but move forward and see.

 

[tolikovski]

if the pH meter is new, you need to properly calibrate it after per-conditioning, as per pH meter instructions. I had to run calibration twice when I got a new probe, then results came in reasonable. You can also make a saturated solution of creme of tartar ( available from a grocery store), just mix enough to have some non-dissolved at the bottom of a jar, for that solution pH should be 3.56. That one I've come across in Iverson book on winemaking. Also I have come across faulty NaOH, not 0.2N, but rather something like 0.45N, so you have to watch out for that. you can experiment with a known acidity sample which you can make yourself with tartaric acid, ie 5g/L for instance. sorry my advice can be already late, something to keep in mind for the next harvest.

 

[JJGDC]

Just a thought... But could the coffee filter be binding up some of the acids? Aren't some of the paper filters slightly alkaline?

Like I said just a thought

JJ