Adjusting acidity of grape must

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NorCal

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@4Score and I do a few tons of grapes each season. We will adjust our typical high pH grapes from this area down to 3.6.pH. We did this last year and two separate wines seem to rebound above 4.0 post ferment/mlf.

I'm not sure if we didn't properly adjust; we measure pH, add tartaric to the must, mix, re measure. We use two pH meters. We make a lot of small acid additions, a lot of mixing, a lot of measuring in all areas of the macro bins.

One thing we have not done is to double check the pH the following morning, before adding yeast. We will add this step this year.

We learned how important it is to do your acid additions preferment; you can add 5g/l preferment, but even 10% of that post ferment makes the wine undrinkable.

Anyone have any other suggestions?
 

geek

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I think rechecking the pH next morning after another stirring will be the right thing to do.

In most cases that is what happens to all of us, I learned to go half way the needed addition and then check a few hours later, it always gets me a different reading after things integrate.
 

Johnd

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@4Score and I do a few tons of grapes each season. We will adjust our typical high pH grapes from this area down to 3.6.pH. We did this last year and two separate wines seem to rebound above 4.0 post ferment/mlf.

I'm not sure if we didn't properly adjust; we measure pH, add tartaric to the must, mix, re measure. We use two pH meters. We make a lot of small acid additions, a lot of mixing, a lot of measuring in all areas of the macro bins.

One thing we have not done is to double check the pH the following morning, before adding yeast. We will add this step this year.

We learned how important it is to do your acid additions preferment; you can add 5g/l preferment, but even 10% of that post ferment makes the wine undrinkable.

Anyone have any other suggestions?
The attached is an excerpt from my Vinmetrica instructions, I've read this in other places as well, and use this process. By blending a sample, you mix not only the juice that you've adjusted, but also the pulp and skins that still have juices locked inside. So maybe when you've adjusted your pH / TA, you're only testing the "free" juice, and as fermentation progresses the "locked up" juice is distributed into the must. The high pH juice that was previously trapped, now pushes your pH back up.

Since I do frozen must, my stuff sits for days warming up with lallzyme ex-v and is usually mush by the time I pitch, plus being frozen breaks it down a lot too. You cats are doing fresh grapes, so maybe the blending will do the trick for you.

IMG_0758.jpg
 

Johny99

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I've seen the blending recommended elsewhere as well. I measure my pH by hand crushing a zip lock baggie with a handful of grapes. I squeeze them down to liberate as much juice and pulp as I can. Then I squeeze the baggie to "press" out as much clean juice as I can into a beaker. I get a pH and TA that correlates better with post fermentation numbers.

I've also done the measure pH everyday during a cold soak and track it method. It does change but I've never let it soak long enough to get .1 stable let alone .01 before I pitch. I usually can't keep it cold enough to keep natural fermentation from starting.

Of note, I'm in brutes not a macrobin. Out of curiosity, how much variation do you get from different parts of the macrobin?
 

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Thank you for the replies. I could definitely see that we are only mixing the acid with the free juice. We get less than .05 difference across the bin. We will be much more careful in measuring pH, at multiple steps in the process.
 

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@NorCal I copied this from BCAWA.

"Whether the grapes are pressed immediately after crushing or let stand on the skins for flavour extraction before pressing, once the juice sample has settled and cleared, the acid and pH readings should be accurate. The same cannot be said for red grapes, however. Most winemakers take their samples immediately after crushing, but the readings are not accurate. Doing a test twenty-four hours later will see an increase in pH of between 0.1 and 0.2 as the direct result of potassium extraction. The TA change will be minimal. A further increase in pH will be observed after pressing due to maceration during fermentation and greater extraction of skin constituents".
 

JohnT

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I have found that preferment acid adjustment is notoriously inaccurate. I like to open ferment on the skins in large vats, pitching yeast 24 hours after crush.

The amount of free run juice and total real volume are not exactly known. Here is what I do and I would be always open to any ideas on how to improve this.

1) When I take a sample, I strain it with a course strainer (stainless steel) and then again through a finer one. There is a lot of pulp and particulates that I feel need to be removed to make the sample more "pure".

2) I then test the PH and TA. I use the PH to tell me if an adjustment is really necessary but adjust using the TA reading. For preferment, I like an acid level of .6 gpl

3) For a 600 liter primary fermenter, I guess that I will have about 100 liters of skins, pulp, and other particulates. This in mind, I adjust to a volume of 500 liters.

4) When adding the acid, I like to add in stages. I'll add some on top, then bring must up from the bottom to cover (using my punch down tool) and repeat several times. Once all acid is added, I continue stirring until my arms are about to give out. This is no easy task as I am adding to thick, freshly crushed must.

5) After waiting an hour or so, I give the must another good stir. I then test again. Most times, the adjustment falls just short of my .6gpl goal. This is fine by me. I just want it close.

6) If needed, I adjust again after fermentation (based on the preference of an acid trial) and adjust SO2 according to that preference.

** again, any suggestions to improve on this method would be greatly appreciated.
 

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You need to measure your TA and adjust for that. For reds you want to be between 6gl - 8gl, I tend to keep mine close to 8gl. Malolactic fermentation will bring this number down between 4gl - 6gl. PH is mostly useful for your SO2 additions and how the SO2 affects your wine. Since your not far from UC Davis I would recommend the wine chemistry class they offer through the UCD Extension. I asked the question about what to do with high PH grapes and they told me to pick earlier.
 

NorCal

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You need to measure your TA and adjust for that. For reds you want to be between 6gl - 8gl, I tend to keep mine close to 8gl. Malolactic fermentation will bring this number down between 4gl - 6gl. PH is mostly useful for your SO2 additions and how the SO2 affects your wine. Since your not far from UC Davis I would recommend the wine chemistry class they offer through the UCD Extension. I asked the question about what to do with high PH grapes and they told me to pick earlier.
Ignore pH and adjust to TA? Not sure that would accomplish my objective, which is to have a microbial stable wine, by having a lower pH (advice given from a masters grad at UCD)
 

NorCal

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Here is the data from last year's vintage. The numbers are post adjustments. All the wine was around 4.0 pH after mlf. Calibrated meter, checked with @4Scores meter. I felt pretty good going into ferment with these numbers and haven't seen them jump that much before from start to post mlf.
 

Tnuscan

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I know I spent more time calibrating and re-calibrating than I wanted too, before and during fermentation. I remember my readings being up then down then up, so much that I really went through a lot of calibrating solution.

I was using two seperate meters too. I should have realized it wasn't the meters. Hind sights always 20/20.

The 24 hour settling out period makes sense. I'll pay better attention next time, and keep more informative notes.This has made me think back and think ahead.
 

fishnchris

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If it taste good, then drink it. I learned a lot from the classes UCD offers and would recommend them to everyone. Lodi wine labs is also a great resource. Their not far away from you and can run a complete panel on your juice. You can do what the French do and use food grade sulfuric acid to lower the Ph. It's illegal for commercial winery's in the USA but not for home winemakers. Cheers!
 

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@4Score and I do a few tons of grapes each season. We will adjust our typical high pH grapes from this area down to 3.6.pH. We did this last year and two separate wines seem to rebound above 4.0 post ferment/mlf.

I'm not sure if we didn't properly adjust; we measure pH, add tartaric to the must, mix, re measure. We use two pH meters. We make a lot of small acid additions, a lot of mixing, a lot of measuring in all areas of the macro bins.

One thing we have not done is to double check the pH the following morning, before adding yeast. We will add this step this year.

We learned how important it is to do your acid additions preferment; you can add 5g/l preferment, but even 10% of that post ferment makes the wine undrinkable.

Anyone have any other suggestions?
Do you feel it is from the solids not settling, or do you have another theory.
 

NorCal

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We do a gentle crush and the amount of liquid then vs at pressing is maybe 3X. So it would make sense that the adjustment would only be to the free juice and be over stated. We will definitely be checking pH more frequently throughout the process.
 

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I'm doing a chardonnay from frozen juice buckets - 10.5gal. I have only done kit wines up till now so want to make desired adjustments pre-ferment. Any suggestions on desired pre-ferment values for a chardonnay? I've got measured PH of 3.43 and brix of 25.5. Have not done TA test yet. Plan to do MLF after primary with VP41.

Thanks!
-johann
 

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I'm doing a chardonnay from frozen juice buckets - 10.5gal. I have only done kit wines up till now so want to make desired adjustments pre-ferment. Any suggestions on desired pre-ferment values for a chardonnay? I've got measured PH of 3.43 and brix of 25.5. Have not done TA test yet. Plan to do MLF after primary with VP41.



Thanks!
-johann
The pH is a good starting point, it'll raise a tad in AF, which will make your MLF even easier. Depending on where you land, and taste tests, you may end up adding acid later, but that'll be up to your taste buds, not mine. As for the BRIX, that might be a little stiff for a chard, but again here, it's more about your taste. Traditionally, you wouldn't want a chard to clock in at 16%, so if it were mine, I'd be watering back a bit with acidulated water, shooting for a 13% or so ABV.

Post your TA when you get it, just to be sure all is in line.
 
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jburtner

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Ok thanks. I'll check TA later this afternoon. I have two buckets and only tested one so will blend them and let sit for a little while before further measurements.

Cheers!
-johann
 

Johnd

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Ok thanks. I'll check TA later this afternoon. I have two buckets and only tested one so will blend them and let sit for a little while before further measurements.

Cheers!
-johann
Just pop in here if you have any questions, I'm sure somebody will be around to help if you need something.
 

jburtner

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Thanks - I was getting different SG readings from the refractometer and hydrometer so I recal'd the refractometer and the chardonnay comes in @ 23.8 Brix now with TA @ about 7.2.
 
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