VDKs (Vicinal Diketones) are metabolic products of yeasts which form in constant proportions during fermentation. These include diacetyl, which forms in the highest concentration.
It is important to monitor vicinal diketones levels during fermentation, as excessive VDKs production may be a sign of incorrect fermentation, bacterial or wild yeast infection. Furthermore, VDKs concentration plays an important role in the formation of flavour during the beer maturation time.
The systems to test VDKs in beer and wort
Vicinal diketones (VDKs) levels can be measured using CDR BeerLab®, a system which enables you to carry out a wide panel of chemical analyses on beer and water, using a single instrument, in a process that is faster and simpler than traditional methods.
With CDR BeerLab® brewers and breweries of any size can independently carry out brewing process controls without having to rely on external laboratories.
 CDR BEERLAB® |
 CDR BEERLAB® JUNIOR |
|
|---|---|---|
| Analyses |
Beer, Wort and Water: Bitterness (IBU) Fermentable Sugars Alcohol by Volume (ABV) Acetic acid Yeast Vitality Vicinal Diketons (VDKs) Total sulfur dioxide Free Amino Nitrogen by OPA (FAN) Colour Starch pH Lactic Acid (D + L) Polyphenols in beer Alkalinity of water Bicarbonate in Water Calcium in Water Zinc in Water Sulfate in Water Magnesium in Water Potassium in Water Chloride in Water |
Configuration with tailored panel of analyses |
| Simultaneous Sample Analyses | 16 | 3 |
| Multiple Analyses on a Sample |  |
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Method
Test type: End Point.
Time testing: one test 5 minutes + distillation time.
Are possible test sessions with several samples, up to 16 for CDR BeerLab® and 3 for Junior CDR BeerLab®
Correlation curve
The CDR BeerLab® method for the determination of VDKs has good accuracy and is good for analyses requiring distillation and spectrophotometric measurement as is established in the report “Evaluation of new features (VDK, yeast vitality) of the CDR BeerLab® Analyser” performed by the international reference laboratory Campden BRI, innovation, research and technology centre for the food and drinks industry. 5 beer samples were analysed in triplicate for VDKs using the CDR BeerLab® method and the reference UKAS accredited VDK method (Campden BRI Method AM/008 based on Analytica-EBC, 9.24.2, 1999), showed that the results were similar (correlation R2 = 0.99).
Test Principle
The beer sample must be distilled. Vicinal diketones contained in the distillate react with an alpha-naphthol and creatine solution to form a coloured complex which absorbs at 520mm. The extent of absorption is proportional to concentration.
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.
- Codice *300925 – The kit, designed for 10 tests
- Codice *300930 – The kit, designed for 100 tests
The reagents have a shelf-life of 6 months.
Check out the key points about Diacetyl and VDKs in brewing process
What is the diacetyl taste? What is the effects of diacetyl and other VDKs on the organoleptic profile of a beer? Check out the key points about Diacetyl and VDKs in brewing process.
Download the article to know in-depth VDKs in brewing process»
Processing of Sample
A distillation method is required to carry out the test. De-gas and distil 100 mL. Recover the first 15 mL, bring to 25 mL and analyse using the instrument.
Measuring Range
| Analysis | Measuring range | Resolution | Repeatability |
|---|---|---|---|
| Vicinal Diketones (VDKs) | 0.05 – 2 ppm | 0.01 ppm | 0.03 ppm |
