Rapid protocol
Assess glucan-related risks
Degradation of both simple and complex pectic polysaccharide chains, as well as glucans from rotten grapes, will improve filtration, speed up and enhance clarification after fining. A negative glucan test is mandatory, and the winemaker should follow up properly after enzyme addition at the right dose and contact time.
A quick test will show glucan levels > 15 mg/L.
For levels between 3 and 15 mg/L, a modified test can be done.
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Glucans may be difficult to detect in a non-depectinised must when their levels are low. It is recommended to conduct the test on the must after settling or on the wine.
How to do the glucan test
Option 1: simple test
1. Prepare the acidified alcohol solution
Ethanol 96% acidified with 1% concentrated hydrochloric acid.
2. Prepare the must or wine to be tested
If the must is charged with solid particles, a coarse filtration on paper is recommended.
3. Add the solution to the must or wine
In a test tube, add 2 volumes of the must and 1 volume of the prepared solution of acidified alcohol and gently mix.
4. Results: If white or grey fibres appear, the test is positive. Glucans are present at >15 mg/L.
The pictures here show results in white, rosé, and red wines with, on the left, no glucan and, on the right, confirmed glucan.
Option 2: Modified glucan test for glucan level between 3 and 15 mg/L
1. Centrifuge the first test or directly the wine or must at 3 000 revolutions per minute for 10-15 minutes.
2. Dissolve the sediment from centrifugation with 5 mL of distilled water, then add 5 mL of acidified alcohol.
3. Results: after 4 minutes, if filaments or small flakes appear, the presence of glucan is confirmed. The results can appear within 1 hour, so check in an hour.