pH lowering, lessons learned

[DaveMcC]

I notice some comments, observations and questions about pH adjustments in must from time to time. Last year I overshot additions of tartaric acid and wound up with a must of 2.68 and had to correct with bicarbonate to get it back up. What a mess. Wine turned out OK and even took a gold medal eventually at one of the amateur competitions. This year, my must pH just measured in at 3.99. I added 112 grams of tartaric acid (dry) to about 40 gallons of must (150 L), which was less than a third of what the usually recommended 1g/L called for to get the must down to 3.50 or so. After my addition, the pH levels just measured at 3.38, quite acceptable. S.G. initially was a whopping 1.128, and I added a L of distilled water and got it down to 1.120 and may dilute a bit further.

I know that there are a few variables in pH adjustments; buffering capacity of the grape must variety, S.G., temperature, etc. I just wish that there were some better estimations out there, which reflected more realistic "in the field" levels as it seems almost everyone overshoots the recommended dosages. Just some observations.

 

[Vern]

When I started making wine and adjustments to must , I made the same mistakes. Now when making any adjustments I start with 25% of recommendations and retest to verify results.

 

[Johnd]

Before making additions to an entire batch, do a short, quick bench trial, it'll give you an indication of what to expect from your current must. Take 5 liters of your must, add a small, measured, known amount to the must and check to see the effects of that addition. Work with small additions until you hit your target, then you'll know how many grams is took to adjust 5 liters of must. From there, it's simple math to determine what you need for the rest of the must. Even then, don't dump it all in at once, go slow and take your time.

 

[DaveMcC]

Before making additions to an entire batch, do a short, quick bench trial, it'll give you an indication of what to expect from your current must. Take 5 liters of your must, add a small, measured, known amount to the must and check to see the effects of that addition. Work with small additions until you hit your target, then you'll know how many grams is took to adjust 5 liters of must. From there, it's simple math to determine what you need for the rest of the must. Even then, don't dump it all in at once, go slow and take your time.

I think that the bench trial process is a good one, but it seems pretty consistent that even with all the variables, the 1g/L ratio to lower pH by .1 is way too much for everyone. If I had followed that target, I would have dumped about 600g, not the 112g I started with. Lessons learned last year.

My starting ratio this time was about 1g/L (112g/150L) which lowered the pH by .6 (3.99 down to 3.38) not .1. I wonder also if this formula deals with just the liquid wine, and not the total must, including solids in suspension.

 

[Raptor99]

When I started making wine and adjustments to must , I made the same mistakes.

Been there, done that.

I think that the bench trial process is a good one, but it seems pretty consistent that even with all the variables, the 1g/L ratio to lower pH by .1 is way too much for everyone.

I don't think that there is a simple reliable ratio because there are too many variables. "Buffering" is sometimes mentioned in this context. If I remember my high school chemistry, a buffer will keep the solution at a certain pH until the buffer chemical is exhausted. That means that as you add acid (or bicarbonate) a little at a time, nothing changes for a while and then all of a sudden with the next addition the pH changes.

I'm not sure whether there are naturally occuring pH buffers in wine, but mead makers often talk about the buffering effect of honey.

I think that he best approaches are bench testing and adding very small amounts a little at a time.

 

[Johnd]

I think that the bench trial process is a good one, but it seems pretty consistent that even with all the variables, the 1g/L ratio to lower pH by .1 is way too much for everyone. If I had followed that target, I would have dumped about 600g, not the 112g I started with. Lessons learned last year.

My starting ratio this time was about 1g/L (112g/150L) which lowered the pH by .6 (3.99 down to 3.38) not .1. I wonder also if this formula deals with just the liquid wine, and not the total must, including solids in suspension.

Remember that your calculations / adjustments should be based upon the quantity of liquid (juice) in your must, not the total volume of must. For my purposes, I’ve always used 60% as my adjustment factor. IE: for 100 gallons of must, there’s 60 gallons of juice, base your additions on the liquid, exclusive of the solids, since the solids won’t absorb any of your added chemicals. Further complicating the issue, there’s still juice sealed up in the pulp and in uncrushed berries that hasn’t been released yet, your chems don’t dissolve into that unreleased juice either. All that said, I do agree with you that it’s not an exact science at all, and slow, small and steady on the additions will keep our adjustments from going overboard.

 

[bjoll001]

I notice some comments, observations and questions about pH adjustments in must from time to time. Last year I overshot additions of tartaric acid and wound up with a must of 2.68 and had to correct with bicarbonate to get it back up. What a mess. Wine turned out OK and even took a gold medal eventually at one of the amateur competitions. This year, my must pH just measured in at 3.99. I added 112 grams of tartaric acid (dry) to about 40 gallons of must (150 L), which was less than a third of what the usually recommended 1g/L called for to get the must down to 3.50 or so. After my addition, the pH levels just measured at 3.38, quite acceptable. S.G. initially was a whopping 1.128, and I added a L of distilled water and got it down to 1.120 and may dilute a bit further.

I know that there are a few variables in pH adjustments; buffering capacity of the grape must variety, S.G., temperature, etc. I just wish that there were some better estimations out there, which reflected more realistic "in the field" levels as it seems almost everyone overshoots the recommended dosages. Just some observations.

Ok dude, here is the answer to your issues, maybe. lol

Do not trust the 1g/L recommendation for changing pH or TA. In the past I would use that but add only 2/3 of that the calculation to the must and it still was overshooting the pH. I learned the best way to get the most accurate (although no perfect) correction is to do a bench trial s described below.

Strain 1 liter of must juice.

Add tartaric acid to this 1 L sample 0.5 g at a time and check pH each time. when it gets to the pH you desire, add that amount of tartaric acid to must.

Example of my Cab Franc this year:

My numbers were pH: 3.98 (Yikes) and TA: 6.2

For my practice, I like to end up with a pH of around 3.6 plus or minus 5. I expect fermentation and Malolactic fermentation to raise the pH possibly .15-.3 depending on the variability of the Must etc.

3.98 way too high for stability

I do bench trials always now to see how much tartaric acid to put in as estimating with equations does not give accurate results

I double or triple strain 1 liter of juice from the must and add 0.5 g tartacic acid at a time, mix and take pH every 0.5 g until I reach my target

pH bench trial results:
0.5 g: 3.87
1 g: 3.73
1.5 g: 3.61
2 g : 3.51 (TA: 8.4)

Choosing from these results is dealer's choice and gives options. For me I chose the 2 g/l option to get the pH in the 3.5 range as I know it “should” go up from fermentation, Malolactic fermentation, tartaric acid naturally falling out of solution and hopefully end up around 3.6-3.7. If it stays in the 3.5-3.6 range I am fine also as many great European wines are in that range as long as it is not too tart (I taste the juice). I have found with experience that adjustments of the must are well tolerated much better than later adjustments.

The way I calculate the must addition

pounds of grapes/ 15.5 = approximate amount of pressed juice/wine after fermentation.

So if you have 495 lbs grapes such I have for the cab franc, here is the calculation

495/15.5= 31.93 gallons juice.

31.93 gal x 3.785 L/Gal = 120.86 L of juice

120.86 L x 2 g/L = 241.72 g

so add 241.72 grams tartaric acid to the must then check pH later

Testing the Cab Franc Must a few days after adding the tartaric acid gives pH 3.50 to 3.58 depending on what part of the must tested (not perfectly homogenized) which is the range I like around starting fermentation. Luckily it does not taste tart either.

Now time will tell how much this will change and turn out but that is the fun of it as long as it is not overshot.

The Cab Franc today is almost done fermenting, Brix -0.3 one fermentation vessel an 0.3 other fermentation vessel. Wine not tasting tart despite the additions but very smooth. After I press tomorrow or the next day, I will recheck pH to see where it is at when the wine is more homogenized. but I expect everything to be on point.

Summary, do bench trial as discussed and you will get closer to real world result. Not perfect but much better than assuming the 1 g/l will reduce pH by 0.1 and increase the TA by 1 g/L as the books say.

 

[Rice_Guy]

Before making additions to an entire batch, do a short, quick bench trial, it'll give you an indication of what to expect from your current must. Take 5 liters of your must, add a small, measured, known amount to the must and check to see the effects of that addition.

FYI: the juice from CACTUS PEARs.
Gravity . .1.026 , , , , pH . . . . . 4.69 , , , , , TA . . . . . .0.12%
View attachment 68711
your question about a recipe ,, how much acid for a cactus pear wine?
. . . suggested target for a country wine . . . .
pH 3.2 to 3.6 with a TA of 0.65 to 0.75% , , , a dry wine
pH 3.0 to 3.5 with a TA of 0.7 to 0.85%, , , , a sweet table wine
* acid is roughly 4 grams per level teaspoonful therefore I would add at least four and likely as much as six teaspoons per gallon of this juice. ,,, add before you can the juice, the food plant rules are if the pH is below 4.0 you could use a boiling water bath.
* metabisulphite in the primary I use up to .2 gram per gallon and racking 0.1 gram per gallon, (a Campden tablet is also metabisulphite and is good for a five or six gallon carboy)
* sugar on this sample was approximately 6.25% and my goal would bring it up to a gravity of 1.090, AKA 25 or 26%
,,,, cactus is an interesting project ,,,,

I would do a lab bench trial with 100 ml and titrate against a 1/10 tartaric acid solution.