Heat stability test uses 30 mL of filtered sample heated to 80°C 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. Commercial Services offers both checks to enable you to make the most informed decision.
Commercial Services’ cold stability method uses 100 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.
We can also isolate and identify crystals, providing that there is sufficient precipitate to evaluate.
Bentonite fining trials
Commercial Services can assist you to determine the optimum bentonite addition for your wine, which 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) and turbidity meter.
|Prices per analysis|
|Analysis||Per Sample (excluding GST)||Volume required||Target response time|
|Heat stability||$30||100 mL||48 hrs|
|Cold stability||$23||200 mL||96 hrs|
|Stability package||$40||300 mL||96 hrs|
|Bentonite trial including three additions||$90||2 x 750 mL bottles
Bentonite required – 20 g
For more information, please contact AWRI Commercial Services on (08) 8313 6600 or e-mail firstname.lastname@example.org