Anthocyanins are polyphenols present in the skin of grapes, whose colour changes according to the acidity of the surrounding environment. Anthocyanins are not very soluble in must and water, but very soluble in alcohol produced during fermentation. The colour of the future wine therefore depends on the degree of ripeness and on the duration of maceration of the skins. In addition, the concentration of polyphenols strongly influences the stability of a red wine during ageing. Therefore, in the case of a red wine, it is important to take into account the phenolic maturity of the grapes when choosing the harvest period.
The method considered to be the reference method for the determination of phenolic maturity (Glories method) is very time-consuming because it requires a long extraction and sample preparation phase. In addition, it is necessary that the analyses be carried out by an operator specialised in laboratory techniques.
The CDR WineLab® method for the determination of Anthocyanins in grapes and therefore of phenolic maturity optimizes the Glories method in order to make it even simpler, faster and more accurate.
The Analyzers CDR WineLab® for determining Anthocyanins on Grape
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.
Method
Test type: End Point.
Time testing: extraction 30 minutes – analysis 6 minutes.
Analysis sessions with several samples are possible, up to a maximum of 16 tests for CDR WineLab® and 3 tests for CDR WineLab Junior®.
Correlation curve
The correlation curve of the CDR WineLab® instrument, carried out in comparison to the Glories reference method, confirmed an excellent system linearity over the entire measuring range.
Test Principle
The total Anthocyanins present in the wine in must and grapes, in a very acidic environment and through the action of a concentrated SO2-based reagent, undergo a discoloration that is measured at 520 nm at end point. This discoloration is directly proportional to the concentration in the sample expressed in mg/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 *300459: 10 tests
Code *300336: 100 tests
The reagents have a shelf-life of 6 months
Sample Processing
Technique of extraction from grapes:
- Select a specific row from which to collect on both sides a total of 200-300 g of berries by sampling them as randomly as possible. Always use the selected row for the following samples in order to have a better representability of the sample.
- Grind the sample of grapes in the mixer for 1 minute.
- Take two samples, each of 6 g, and place them in the disposable containers provided for this purpose.
- Add 6 ml of solution A with pH 1 to the first sample.
- Add 6 ml of solution B with pH 3,2 to the second sample.
- Close the containers and wait 30 minutes. Mix them manually a couple of times.
- Centrifuge the suspensions. 0.5 mL of filtered sample is sufficient for the test.
Measuring Range
| Test | Measuring Range | Resolution | Repeatability |
|---|---|---|---|
| Anthocyanin grapes | 10 - 1000 mg/L of Cyanidin 3-O-glucoside | 1 mg/L of Cyanidin 3-O-glucoside | 6 mg/L of Cyanidin 3-O-glucoside |
