Figure 2: New face: An electronic ebulliometer has taken the measurement of wine into the cyber age to help winemakers test the level of alcohol in their production.
So rather than calibrating the ebulliometer with distilled water, a better approach is to calibrate it with a stable wine sample of known alcohol concentration, otherwise known as a “standard wine”. This is best obtained from a NATA accredited laboratory. This standard wine will be much better matrix-matched to your samples and have an alcohol concentration closer to your samples, thus improving accuracy (see Figure 4).
OTHER TECHNIQUES FOR MEASURING ALCOHOL: DISTILLATION Another technique for measuring alcohol in wine that is suitable for small to medium wineries is distillation. The cost for setting up and operating this is about the same as for ebulliometry, however this technique is: • More accurate • Officially recognised by the OIV (inferring it is of sufficient accuracy) • Has very low consumable costs The major disadvantages of the distillation technique are: • It is more time consuming than ebulliometry • It requires better technical skills • If used with a pycnometer (weighing bottle) it requires an accurate balance • If used with a hydrometer then this requires calibration • It is glassware-based and so the apparatus is more fragile The best technique (but most likely out of the range of most small to medium wineries due to the A$20k price tag) is a near infrared (NIR) spectrometer. This is the method we use in our laboratories.
September 2014 – Issue 608
For further information, please contact Kauri NZ Tel: 0800 KAURIWINE NZ Fax: 04 910 7415 Email: winery@kauri.co.nz
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Grapegrower & Winemaker
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