Screening tests for commonly used winemaking chemicals and processing aids

Disclaimer
Please note that these are not definitive tests, however are merely basic sensory tests in most instances, designed to provide an indication to whether or not the substance contains obvious impurities and or contains obvious taints. Where possible, these tests should be conducted in conjunction with another person and compared to Analytical Grade comparable chemicals. (For example, when screening tartaric acid, you should use Analar L-tartaric acid as a comparable control.) If there is any doubt on the results, or how to interpret the results, please contact the AWRI Helpdesk on 8313 6600.

Please be aware of the potential safety hazards when handling chemicals, and in particular diatomaceous earth and bentonite. Appropriate breathing apparatus must be worn when handling these two products.

Please be aware that some winemaking additives (such as bentonite and gelatine) do have unique aromas. We do recommend that you first familiarise yourself with a number of these products, to expose yourself to as many of the different types and unique aromas that they exhibit.

Assessing chemicals and additives

The following table is a simple template that can be used for recording sampling and testing requirements for all winemaking chemicals and additives upon receival.

Examples on how this could be used are provided below.

Batch numbers should ALWAYS be recorded upon receival, and holdback samples should be taken at the same time as the testing samples. Holdback sample size will be the same as the testing sample size.

 

Material
Sampling
requirement
Testing
required
Test
method
Holdback
sample
(yes/no)
L-Ascorbic Acid 200g of each batch Sensory assessment Yes
Bentonite 1 kg of each batch Sensory assessment Yes
Carbon 200g per batch Sensory assessment Yes
Citric 200g per batch Sensory assessment Yes
Gelatine
(solid)
200g per batch Sensory assessment Yes
Hose 1 foot per hose Sensory assessment Yes
PVPP 200g Sensory assessment Yes
L-Tartaric
acid
200g per batch Optical rotation and
Sensory assessment
Yes
Yeast Hulls 200g per batch Sensory assessment Yes

Bentonite

**Safety note. Take care when handling. Wear appropriate breathing protection, due to fine dust hazard.

“Bentonite should not have any undesirable odour (e.g. mould), and should not change the taste of wine.” International Oenological Codex, 2006

Screening procedure: Make up a 10% slurry of bentonite. Simply place some of this bentonite in a glass and assess the aroma for any mouldy odour and any taints.

Interpretation: If the bentonite exhibits mouldy odours or taints, then the bentonite is unsuitable for use. (2006 OIV Oenological Codex)

Copper sulfate (CuSO4.5H2O)

Screening procedure: Dissolve 10g of copper sulfate in 50 mL of clean water. Swirl and assess the AROMA ONLY of the solution. DO NOT TASTE.

Interpretation: The solution should be clear and free from turbidity and taint aromas. (2006 OIV Oenological Codex)

Cream of tartar/Potassium hydrogen tartrate (KHT)

It has become evident recently that the use of impure cream of tartar (DL-KHT) for cold stabilizing white wines can lead to calcium DL tartrate deposits. Presently the only way to determine the purity of cream of tartar is to determine the optical rotation of the material. This analysis can be conducted by the AWRIs Analytical Service. Please contact AWRI Commercial Services for further information.

Diatomaceous Earth

**Safety note. Take care when handling. Wear appropriate breathing protection, due to fine dust hazard.

Screening procedure: Place 2.5 g of DE into 1L of wine. Mix and leave for 24 hours.
Compare the taste of this wine to the same control wine that does not contain any DE.

Interpretation: The DE should not impart any odour or foreign taste to the wine. (2006 OIV Oenological Codex)

Gelatine (solid)

Screening procedure: Make up a 5% solution in clean warm water. Ensure that the solution is mixed well before assessing the aroma and taste.

Interpretation: The solution should not exhibit any off-odour or foreign taste.

L-Tartaric acid

Foreign Matter Test: Dissolve 1 g of tartaric acid in 1 mL of clean water or 4 mL of 95% v/v ethanol.

Interpretation: L-Tartaric acid should be soluble in its own weight of water and in four times its weight of ethanol, (i.e. no residue should be apparent). (2006 OIV Oenological Codex)

DL and D tartaric acid are not suitable for use in winemaking. DL Tartaric Acid will not dissolve in its own weight of water, however D Tartaric will. The only way to distinguish between D Tartaric acid and L tartaric acid, is by optical rotation. This service is offered by the AWRIs Analytical Service. Please contact Eric Wilkes for further information.

Winemaking transfer hoses

Screening procedure: Use approximately 300mm of hose. Attach a stainless steel plug to one end of the hose and secure with a clamp to make an effective seal.

  • Carefully fill with 3% NaOH and soak for approximately 10 minutes. Thoroughly rinse off NaOH with water.
  • Using the following table as a guide, fill the hose with wine simulant (~14% ethanol and water solution), seal with a stainless steel plug or alfoil and soak for 5-7 days.

 

Hose Diameter
Volume of wine simulant

38mm

200

75mm

200

100mm

400
  • After 5-7 days, mix thoroughly, divide into 2 equal portions and place in clean glass bottles.
  • Chlorinate one of the samples by adding approximately 50 mg/L of chlorine (sodium hypochlorite), mix and allow to stand for 24hrs.

Interpretation: Assess the aroma of both samples as well as noting any discolouration of the sample and the colour and turbidity of the extraction medium.

Yeast hulls

Screening procedure: Place 5 g of yeast hulls into 50 ml of 95% ethanol and stir for 24 hours. Dilute this solution down to approximately 30% v/v ethanol by adding 16 ml of the solution to 50 ml of water.

Interpretation: The yeast hulls should not impart any odour or foreign taste to the wine.