Lab Tip: De-gas your TA sample to get accurate results

It is good practice in a winery lab to always degas wine samples prior to analysis of titratable acidity (TA).

This is of particular importance at this time of year for wines that have just finished primary or secondary fermentation, as they can contain a high concentration of dissolved carbon dioxide. In wine, carbon dioxide exists as carbonic acid, which interferes in the measurement of TA to give erroneously high values.

Here are a few options for degassing samples:

• Add about 100mL of wine to a chner vacuum flask, insert the stopper, attach the side arm to a vacuum pump and gently shake for 5 minutes. Alternatively, add a magnetic stirrer bar to the flask and place it on a magnetic stirrer to agitate the sample.
• Heating a sample will drive off the carbon dioxide. Boil the sample for a few seconds only and then allow it to come back to room temperature before analysing. It is important with this approach that you accurately measure the sample required before heating, do not heat a larger volume of wine and then sub-sample from it.
• Sparge the wine with nitrogen gas. This is a common method used with automatic titrator systems. A porous tip on the end of a tube connected to a nitrogen gas bottle is inserted in the sample and automatically sparges the sample prior to titration.