The Australian Wine Research Institute’s Analytical Service - Analyses

Acid analysis

pH
pH on wine, juice, water and other liquid samples is analysed using either a calibrated pH meter and combination Orion electrode or a FOSS FTIR Winescan.

Titratable acid
Titratable acidity is measured on a degassed sample at the endpoint of 8.2 for Australian requirements and 7.0 to fulfil the requirements of the European Union. Both results are expressed as g/L tartaric acid. Tartaric acid can also be measured using HPLC or a FOSS FTIR Winescan.

Volatile acid
Volatile acidity is measured by a FOSS FTIR Winescan or as acetic acid by enzymatic assay. Acetic acid makes up a large proportion of the volatile acidity and is used as the routine measure of volatile acidity. Acetic acid can also be measured using HPLC.

The traditional method for volatile acidity involves using distillation (via a modified Markham still) after removal of sulphur dioxide using hydrogen peroxide, and titration with standardised sodium hydroxide. This method includes small amounts of other volatile acids. In the event of a dispute the traditional method will prevail.

Malic acid
This analysis is used for monitoring the progress of malolactic fermentation during winemaking. The method is specific for L-malic acid, which is the naturally occurring isomer in grapes. It should be noted that commercial malic acid supplied to the wine industry as an acidulant, may contain D-malic acid in addition to, or instead of, L-malic acid. Analysis by HPLC in conjunction with enzymatic analysis will determine proportions of both D-malic and L-malic acid in samples

Lactic acid
This analysis is also used for monitoring the progress of malolactic fermentation during winemaking and, as for malic acid, the enzymatic analysis is specific for L-lactic acid.

Citric acid
Citric acid analysis is performed as part of an export analysis certificate for bulk wine destined for the European Union. As the limit for any wine exported to the EU is 1.0 g/L, analysis to confirm any addition of citric acid is recommended.

Organic acid profile (by HPLC)
This high performance liquid chromatography method measures citric, tartaric, malic, lactic, acetic and succinic acids simultaneously and provides a more economical option if several organic acids are required. Glucose, fructose and glycerol can also be measured simultaneously.

Other acids
If you would like analysis for the less common acids such as benzoic or oxalic acids, please contact us for more details. For ascorbic and erythorbic acids, please see the section on preservatives and anti-oxidants.