The Australian Wine Research Institute’s Analytical Service - Analyses

Stability analysis and fining trials

Heat stability

Our heat stability test uses 20 mL of filtered sample heated to 80ºC for six hours. A control is also prepared, but not heated. After this heating, the sample is quickly cooled and viewed under very strong light with a narrow aperture. If a visible beam of light passes through the sample, it is considered a fail. We also measure turbidity using nephelometry. The arbitrary pass point for stability is a turbidity difference of less than 0.5 units when compared with an unheated filtered sample. There are many exceptions to this and it is always wise to perform a visual check of the samples. The Analytical Service offers both checks to enable you to make the most informed decision.

Prices per sample (excluding GST)

Bentonite fining trials

The Analytical Service can assist you to determine the optimum bentonite addition for your wine, that removes the risk of haze formation whilst minimising flavour loss. Your own bentonite is used to prevent the effects of brand and batch variation and we will also help you to decide which fining rates to assess. All trials are measured by visual inspection (using the method described for heat stability). Turbidity measurements using nephelometry may also be used. We can also perform the trial in stages that enables you to narrow your addition rate. Normally the initial trial includes three additions of bentonite at different concentrations. Extra additions will attract additional costs.

Please note: You must supply 20 grams of your own bentonite with the samples.

Cold stability

Our cold stability method uses 200 mL of filtered sample immersed in a -4°C liquid bath for 72 hours. The sample is then viewed under strong light to determine the presence or absence of crystals. The sample is assessed at cold and ambient temperatures as some phenolic material, ie amorphous pigments and tannins, may form a transient precipitate in some red wines. Allowing the sample to warm to ambient temperature usually results in their resolubilisation, and this allows precipitates to be differentiated from potassium bitartrate crystals. If a transient precipitate is detected, it will be noted on your report.

We can also isolate and identify crystals, providing that there is sufficient precipitate to evaluate.