different acid measurements

[elisabeth]

I am relatively new to wine making but am beginning to try and test the acid levels (accurately) in my wine and compensate if needed. My last grapes I bought were from our local university extenstion and he said the titratable acid was 7.51 g/l. I'm not sure if my little kit and his more extensive ability to test are testing the same thing because after I tested my already fermented wine the acid level seemed to low. My acid level from that little testing kit home winemakers buy (sodium hydroxide and that color solution) was .4 ish. So, what did he test and what did I test? I never quite trust my testing. I haven't put it on oak yet but I have fined it and put it in cold storage. The cab seems pretty tasty, the sangiovese very light and the sirah, heck, I can't tell about it. tart maybe.

Thanks for your help,elisabeth

 

[geocorn]

Elisabeth,


Give me a day or two. I need to do some research.

 

[Joseph1]

Elisabeth,<?amespace prefix = o ns = "urnchemas-microsoft-comfficeffice" />

I believe you are both measuring the same thing. Based upon my experience with the testing kits, your reading of .4 ish is about 4.0 g/l. The kits are measuring a percent of concentration (0.4%).

There can be a number of reasons for the different readings. First, the university extension service may have used a pH meter to determine the end point rather than the color solution. The color change at the end point for a red wine is difficult to see. With a pH meter, sodium hydroxide is slowly added until the meter reads 8.2 and you are at the end point.

Second, finished wines have a lower acid level than the juice. The fermentation process can reduce the acid by 0.5 to 1.0 g/l. If the wine had gone through malolactic fermentation, an additional reduction of 0.5 to 2.0 g/l or more could have occurred.

To determine the end point in a red wine you might want to try the “white tile” method described in this article: http://www.vawa.net/articles/acid1.shtml

I have never been confident in my ability to see the end point.


Joseph

 

[geocorn]

Thank you, Joseph!

 

[masta]

I am starting to make some meads and have ordered a pH meter to help with testing since I have read that the pH in honey is not stable and tends to fall during the fermentation.


Here is a link to a a small handheld unit I ordered


http://www.aquaticeco.com/index.cfm/fuseaction/product.detai l/iid/834/cid/136Edited by: masta

 

[elisabeth]

Hey, thank you very much for the info. I was surprized that it lowered it that much and a little disappointed because I understand the wine might be a little more stable with a higher acid content. Oh well! Evrything I have read says that you should add the acid BEFORE fermentation so that the flavor is not ruined. Do you have anymore suggestions? Grazie E.

 

[Joseph1]

Elisabeth,<?amespace prefix = o ns = "urnchemas-microsoft-comfficeffice" />

In his book “Home Winemaking Step by Step”, Jon Iverson indicates that it is possible to increase the acidity post fermentation up to 0.15% (1.5 g/l) without an adverse affect on taste. It can be done during bulk aging, increasing a little each time the wine is racked, rather than a single large adjustment.

Test and taste before each addition. I would aim for a balanced taste rather than a number. Too little acid and a wine will taste flat; too much acid and a wine will taste tart. I have more confidence in my taste buds than I do in my acid testing ability.

Joseph