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Titration error
Hi:
I've been having a pretty consistent problem with titrating white juice before fermentation, adding tartaric acid based on the results, and then titrating after fermentation that the TA level is way too high. Latest example: Pinot Blanc juice measured at 4g/L, acid added to raise to 6.5g/L, now measured at 8g/L after relatively cold (around 15C) fermentation. I really don't know what's going on because: - I'm using the same method (pH meter to 8.2) before and after fermentation; - the juice is fresh, so all acid should be measurable before fermentation; - it can't be sodium hydroxide losing strength because then the measurement would be artificially higher, not lower; - the error seems to be consistent, so that cancels any possible accidents, like wrong sample size. I'm stumped at this point, and I'd really appreciate any help on this, as I don't enjoy wines that are too heavy on acid. Thx, Pp |
Titration error
"pp" > wrote in message om... > Hi: > > I've been having a pretty consistent problem with titrating white > juice before fermentation, adding tartaric acid based on the results, > and then titrating after fermentation that the TA level is way too > high. Latest example: Pinot Blanc juice measured at 4g/L, acid added > to raise to 6.5g/L, now measured at 8g/L after relatively cold (around > 15C) fermentation. I really don't know what's going on because: > - I'm using the same method (pH meter to 8.2) before and after > fermentation; > - the juice is fresh, so all acid should be measurable before > fermentation; > - it can't be sodium hydroxide losing strength because then the > measurement would be artificially higher, not lower; > - the error seems to be consistent, so that cancels any possible > accidents, like wrong sample size. > > I'm stumped at this point, and I'd really appreciate any help on this, > as I don't enjoy wines that are too heavy on acid. > > Thx, > > Pp Hi Pp, You may not have a measurement error. Acid adjusted, grape fermentations often measure from 0.5 to 1.5 g/l higher after fermentation because yeast produces succinic acid during fermentation. If you chill the wine to 32 degrees or so for a few days, potassium bitartrate will precipitate out of the wine and reduce the titratable acid. Sometimes, the drop in TA due to tartrate precipitation is about equal to the increase in from succinic acid, and the TA of the cold stabilized wine ends up being just about equal to the starting TA. See Margalit, Concepts in Wine Chemistry, page 17. lum |
Titration error
pp wrote "I've been having a pretty consistent problem with titrating white juice before fermentation, adding tartaric acid based on the results, and then titrating after fermentation that the TA level is way too high." Are you sure of the volumes of juice you are working with? Was the starting juice very well mixed before sampling for acid test? Are you sure your acid addition was totally in solution before testing? Is there carbon dioxide still in your fermented wine? Does the wine taste too acid? Bill Frazier Olathe, Kansas |
Titration error
"pp" > wrote in message om... > Hi: > > I've been having a pretty consistent problem with titrating white > juice before fermentation, adding tartaric acid based on the results, > and then titrating after fermentation that the TA level is way too > high. Latest example: Pinot Blanc juice measured at 4g/L, acid added > to raise to 6.5g/L, now measured at 8g/L after relatively cold (around > 15C) fermentation. I really don't know what's going on because: > - I'm using the same method (pH meter to 8.2) before and after > fermentation; > - the juice is fresh, so all acid should be measurable before > fermentation; > - it can't be sodium hydroxide losing strength because then the > measurement would be artificially higher, not lower Sounds to me like that's _exactly_ what you're seeing. You're getting higher measurements than you expected. Still, that's probably not it. I'd guess that you're titrating dissolved CO2 + TA because you didn't degas the sample. Bring the sample just to the boiling point to drive off the CO2 before titrating. Tom S |
Titration error
"Lum" > wrote in message >...
> > Hi Pp, > You may not have a measurement error. Acid adjusted, grape fermentations > often measure from 0.5 to 1.5 g/l higher after fermentation because yeast > produces succinic acid during fermentation. If you chill the wine to 32 > degrees or so for a few days, potassium bitartrate will precipitate out of > the wine and reduce the titratable acid. Sometimes, the drop in TA due to > tartrate precipitation is about equal to the increase in from succinic acid, > and the TA of the cold stabilized wine ends up being just about equal to the > starting TA. See Margalit, Concepts in Wine Chemistry, page 17. > lum Hi Lum: Thanks a lot for this interesting info. I've always thought the acid level is supposed to drop after fermentation by about 0.5g/L on avg. So, if I understand this correctly, after cold fermentation, the acid can actually move in any direction w.r.t to the starting level, depending on the levels of succinic acid generated and bitartrate falling out? And, does this only apply to juice that has had tartaric acid added to it or in general? I'll definitely check out the Margalit reference, only have to hunt it down, which will take some time. Thx, Pp |
Titration error
"Tom S" > wrote in message .com>...
> Sounds to me like that's _exactly_ what you're seeing. You're getting > higher measurements than you expected. > Ah, email/news, no matter how clear I'm trying to be, there is always some crucial bit missing... What I forgot to add was that, based on taste, the second (higher) measurement seems correct. I also remember thinking, after I added the acid on the Pinot B, that it tasted quite tart. I recall you talked in a post a while back about using the taste as the ultimate guide, only I still don't have the right frame of reference for guessing the final balance under all that initial sugar... > Still, that's probably not it. I'd guess that you're titrating dissolved > CO2 + TA because you didn't degas the sample. Bring the sample just to the > boiling point to drive off the CO2 before titrating. > > Tom S Will do. I haven't got any fizziness while sampling, but it definitely would be a good reference point to do a test after degassing. I'll report back. Thx, Pp |
Titration error
"pp" > wrote in message om... > "Lum" > wrote in message >... > > > > Hi Pp, > > You may not have a measurement error. Acid adjusted, grape fermentations > > often measure from 0.5 to 1.5 g/l higher after fermentation because yeast > > produces succinic acid during fermentation. If you chill the wine to 32 > > degrees or so for a few days, potassium bitartrate will precipitate out of > > the wine and reduce the titratable acid. Sometimes, the drop in TA due to > > tartrate precipitation is about equal to the increase in from succinic acid, > > and the TA of the cold stabilized wine ends up being just about equal to the > > starting TA. See Margalit, Concepts in Wine Chemistry, page 17. > > lum > > Hi Lum: > > Thanks a lot for this interesting info. I've always thought the acid > level is supposed to drop after fermentation by about 0.5g/L on avg. > So, if I understand this correctly, after cold fermentation, the acid > can actually move in any direction w.r.t to the starting level, > depending on the levels of succinic acid generated and bitartrate > falling out? Yes. TA can go up, down or stay the same, but not by large amounts (~1 g/l or so). >And, does this only apply to juice that has had tartaric > acid added to it or in general? Succinic acid production is not very dependent on the amount of tartaric acid added, but tartrate precipitation will be greater with larger additions of tartaric acid. > I'll definitely check out the Margalit reference, only have to hunt it > down, which will take some time. > > Thx, > > Pp |
Titration error
Thanks for help, everybody. Per Tom's, Dave's and Bill's suggestion,
I've done another test on the Pinot Blanc, with 2 samples - one degassed and one not. Yes, the degassed sample was lower by 0.5g/L, so my initial post-ferment measurement was indeed artificially higher. I'll watch this from now on. Given the correct value is 7.5g/L, I'm still 1g/L above the expected value of 6.5g/L. This could be the succinic acid, as Lum suggested. But I'm still wondering about the initial measurement - it came at 4g/L, with pH 3.4, but it didn't taste particularly flabby. The juice came in frozen, I've defrosted it, mixed pretty thoroughly and let settle in the fridge for a day, then measured. Is it possible there was some bitartrate in the juice that went back into tartaric acid during fermentation? And if yes, how do I avoid getting this error again - should I heat the initial sample as well? Thx, Pp (pp) wrote in message . com>... > Hi: > > I've been having a pretty consistent problem with titrating white > juice before fermentation, adding tartaric acid based on the results, > and then titrating after fermentation that the TA level is way too > high. Latest example: Pinot Blanc juice measured at 4g/L, acid added > to raise to 6.5g/L, now measured at 8g/L after relatively cold (around > 15C) fermentation. I really don't know what's going on because: > - I'm using the same method (pH meter to 8.2) before and after > fermentation; > - the juice is fresh, so all acid should be measurable before > fermentation; > - it can't be sodium hydroxide losing strength because then the > measurement would be artificially higher, not lower; > - the error seems to be consistent, so that cancels any possible > accidents, like wrong sample size. > > I'm stumped at this point, and I'd really appreciate any help on this, > as I don't enjoy wines that are too heavy on acid. > > Thx, > > Pp |
Titration error
pp wrote "The juice came in frozen, I've defrosted it, mixed pretty thoroughly and let settle in the fridge for a day, then measured. Is it possible there was some bitartrate in the juice that went back into tartaric acid during fermentation? And if yes, how do I avoid getting this error again - should I heat the initial sample as well?" Pp - "The juice came in frozen"...there's your answer. I cold soak and sometimes freeze juice to lower acid in some of my hybrid juice. You can drop a lot of acid out of juice by freezing. I suspect your starting acid measurement was low because of this. Then as the juice warmed up and fermentation proceeded some of that acid went back into solution. To avoid this in the future I would let the juice come to room temperature and stir up very well. Then take several samples and run the TA tests. See how close your titration results are...if all of the acid is in solution your numbers should be very close. Bill Frazier Olathe, Kansas |
Titration error
"William Frazier" > wrote in message >...
> > Pp - "The juice came in frozen"...there's your answer. I cold soak and > sometimes freeze juice to lower acid in some of my hybrid juice. You can > drop a lot of acid out of juice by freezing. I suspect your starting acid > measurement was low because of this. Then as the juice warmed up and > fermentation proceeded some of that acid went back into solution. To avoid > this in the future I would let the juice come to room temperature and stir > up very well. Then take several samples and run the TA tests. See how > close your titration results are...if all of the acid is in solution your > numbers should be very close. > > Bill Frazier > Olathe, Kansas Hi Bill: I thought that's what I did, apart from testing several samples. The juice was at room temperature and I mixed it well. How long do you have to wait for the acid to go back into solution? Also, for clarification - I'd need to take the several samples over some time, right, otherwise I'm just measuring whatever the acid level is at the moment, no? Thx, Pp |
Titration error
Pp. - I should have asked first if the company you bought the juice from
gave you starting Brix (or S.G.), pH and TA test results? If so how did these numbers compare to yours? > I thought that's what I did, apart from testing several samples. The > juice was at room temperature and I mixed it well. How long do you > have to wait for the acid to go back into solution? I don't know how long it would take for acid to redissolve. It's not instantaneous. If I suspected acid had precipitated out of solution and I was real concerned about knowing the actual starting TA I would do one of the following; Let the juice warm to room temperature and stir it up real well. Take 4 or 5 samples from different places in the juice. If the juice is very well mixed the test results should be close even if all precipitated acid is not totally dissolved. As an alternative you could decant the juice off any settled material. This way there would not be anything to redissolve. Then after testing you could adjust TA and be confident you have a valid starting number. Also, for > clarification - I'd need to take the several samples over some time, > right, otherwise I'm just measuring whatever the acid level is at the > moment, no? No. You want to know what the acid level is at the moment before you start fermentation. Take multiple samples so you know if the TA is uniform across the batch of juice. Keep in mind that I'm the type of winemaker that does lots of tests, so I can better understand what happens in the winemaking process. I enjoy the testing and all other aspects of winemaking. The more I learn about wine the more I need to know. Bill Frazier Olathe, Kansas |
Titration error
Bill, thanks for all your help. I had to recheck my notes over the
weekend. First, I had not data from the producer - this juice came from a grower, via a home brew shop connection. The grower crushed and pressed and also added bentonite, as I found out after defrosting. According to my notes, I defrosted the juice in warm bath, mixed and measured Brix, pH, and TA. The TA came at 4.1 g/L, pH 3.51. I added 40g tartaric - estimated the juice volume to somewhere between 20-22L, so ws aiming for around 6g/L. Mixed and put in fridge for a day to settle. Next evening remeasured pH and TA - 3.21 and 6g/L. The TA looked bang on but still low, so I added another 10g/L, bringing the estimated total to 6.5g/L (didn't measure after). Next, I racked the juice off bentonite and added yeast starter. So, that brings me to the point. The juice was cold but unfrozen for more than a day. Also, any bitartrate should at that stage have been in the bentonite sludge, so I'm not sure if the freezing had any effect on the *measured* initial TA level. Anw, I think we can close this off now; I'll just watch this more closely in the future. I totally hear you about this hobby/passion being a constant learning experience. I don't think I've ever made a wine without one or more "blunders" in the process - as the knowledge grows, they just become more esoteric ;) It's fascinating. Til later, Pp "William Frazier" > wrote in message >... > Pp. - I should have asked first if the company you bought the juice from > gave you starting Brix (or S.G.), pH and TA test results? If so how did > these numbers compare to yours? > > > I don't know how long it would take for acid to redissolve. It's not > instantaneous. If I suspected acid had precipitated out of solution and I > was real concerned about knowing the actual starting TA I would do one of > the following; > > Let the juice warm to room temperature and stir it up real well. Take 4 or > 5 samples from different places in the juice. If the juice is very well > mixed the test results should be close even if all precipitated acid is not > totally dissolved. > > As an alternative you could decant the juice off any settled material. This > way there would not be anything to redissolve. Then after testing you could > adjust TA and be confident you have a valid starting number. > > Also, for > > clarification - I'd need to take the several samples over some time, > > right, otherwise I'm just measuring whatever the acid level is at the > > moment, no? > > No. You want to know what the acid level is at the moment before you start > fermentation. Take multiple samples so you know if the TA is uniform across > the batch of juice. Keep in mind that I'm the type of winemaker that does > lots of tests, so I can better understand what happens in the winemaking > process. I enjoy the testing and all other aspects of winemaking. The more > I learn about wine the more I need to know. > > Bill Frazier > Olathe, Kansas |
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