Determination of tannins in wine and must
Tannins are relatively large phenolic polymers that derive from the polymerisation reaction of phenolic monomers. Their reaction with glycoproteins present in saliva determines the sensory sensation of astringency. They are present in all the solid parts of the grape (skins, seeds and stalks), flow into the must during the maceration phase and end up in the wine.
The CDR WineLab® method aims to monitor the concentration of tannins in wine in order to monitor the evolution of these both during alcoholic fermentation and during the micro-oxygenation phase.
The reference method used for comparison (Ribérau-Gayon and Stonestreet 1966) is based on the hydrolysis of these compounds in an acidic environment (Bate-Smith reaction) which releases highly unstable carbocations which precipitate in the form of brown-coloured polymers. The reference method is very complex and requires the sample to remain in a bain-marie at 100°C during the reaction. The reaction time is 30 minutes.
Optimisation of the CDR method reduces reaction time to just 5 minutes using a microwave.
So the CDR WineLab method® optimises the reference method because it reduces the analysis time and is very simple to perform directly in the winery.
In addition, the CDR WineLab® method® optimises the reference method for repeatability: the standard deviation ranges from 0.13 g/L with the reference method to 0.07 g/L with the CDR method.
The determination of tannins is part of a broad analysis panel developed by the CDR laboratories, implemented on CDR WineLab®®, which offers the oenologist a precise and accurate control of both the polyphenolic extraction phase in red wines (maceration), and the subsequent phase of polyphenolic stabilisation (and therefore of colour stabilisation) that occurs with the micro-oxygenation process.
To learn more read ”Controlling Maceration and Micro-oxygenation in the wine-making process“.
The Analyzers CDR WineLab® for determining Tannins in Wine and Must
The system is supplied pre-calibrated and ready for use.
Results are expressed in accordance with the reference method.
It is also possible to standardize the system using samples with a known titration.
The reagents have a shelf-life untill 18 months
The analytical methods are simple: the system does not require an equipped laboratory or skilled staff.
 CDR WINELAB® |
 CDR WINELAB® JUNIOR |
|
|---|---|---|
| Analyses | Wine and Must: Acetic acid (volatile acidity) Fermentable Sugars Total Acidity L-Lactic Acid L-Malic Acid Free sulfur dioxide Total sulfur dioxide Alcohol by Volume Yeast Assimilable Nitrogen (YAN) Gluconic Acid Acetaldehyde (Ethanal) pH Total Polyphenols Index Glycerol Colour (tonality and intensity) Total Polyphenols Total Anthocyanins Polymerised Anthocyanins HCl Index Tannins Catechins Copper |
Configuration with tailored panel of analyses |
| Simultaneous Sample Analyses | 16 | 3 |
| Multiple Analyses on a Sample |  |
– |
Method
Test type: End Point.
Time testing: 5 minutes.
Are possible test sessions with several samples, up to a maximum of 16.
Calibration curve
The correlation curve of the determination of tannins in wine and must with CDR WineLab®, carried out with respect to the reference method Ribérau-Gayon and Stonestreet 1966.
Test Principle
The method developed by CDR for the determination of tannins is aimed exclusively at the category of condensed tannins. Normally, the concentration of condensed tannins ranges from approximately 1 to 4 g/L.
The CDR WineLab® method is based on the hydrolysis of tannins in an acidic environment (Bate-Smith reaction) which releases highly unstable carbocations which precipitate in the form of brown-coloured polymers when exposed to high temperatures. For this reason the CDR WineLab® method involves using a microwave to heat the tubes inside which the tannin hydrolysis reaction takes place.
The 520 nm precipitate reading performed with the CDR WineLab® instrument is directly proportional to the concentration of tannins in the sample, which the instrument returns at the end of the analysis in g/L.
Reagent test Kits
The reagents are packaged in foil pouches containing 10 tubes useful to perform 10 analyses.
This is the minimum package that allows the use of CDR systems even to those who need to make a few analyses, thus not wasting reagents.
There are also boxes of 100 tests, however, packaged in 10 bags of 10 tubes containing the reagent.
Code. *300xxx: 10 tests
Code. *300xxx : 100 tests (10 packages of 10 tests)
The reagents have a shelf-life of 8 months.
Sample Processing
Wine: Use the wine as it is after centrifugation.
Must: Use the must as it is after centrifugation and degassing.
Measuring Range
| Test | Measuring range | Resolution | Repeatability |
|---|---|---|---|
| Tannins | 0.3 – 5.5 g/L | 0. g/L | 0.1 g/L |
