Category: VDK's

VDK+ Test Kit: What does it mean when you see a dark circle?

6/15/2022

First off, make sure you take photos so that we can help troubleshoot! There are some troubleshooting steps we can take to diagnose what is happening. It is possible that this is a real result. 2,3-pentanedione and/or acetoin, which are vicinal diketones (VDK's) similar to 2,3-butanedione (diacetyl) sometimes show up as a dark circle, especially with certain types of yeast. You won't necessarily detect any diacetyl via sensory because 2,3-pentanedione and acetoin are not as potent as diacetyl. However, before we can say that, I want to make sure everything else about the test is running smoothly.

Are you writing with Sharpie on the lid/cap? That can bleed into the filter paper.
Have you run a water blank? Run the test with 10 mL of distilled water (or even tap water). Do you still see the dark circle?
When you see the dark circle, can you detect any diacetyl sensory-wise? That will help lead troubleshooting.
Is the height of the water in the water bath above the level of the liquid in the vials?
Is the dark circle occurring in real beer samples or samples with controls? If controls, what controls are you using? We have found that controls from Aroxa do not actually contain diacetyl and manifest as that dark circle because they are using one of the other VDKs mentioned above.
Have you measured the actual water temp of the water bath? I have seen the dark circle when the water bath is hotter than 70C.

VDK+ Test Kit: Helpful Tips

5/17/2022

Make sure all chemicals are being stored correctly. All chemicals are labeled with how they should be stored but here is a quick run down
- Reagent A - room temp in dark
- Reagent B - before reagent C is mixed in - room temp
- Reagent C - before mixed with reagent B - room temp
- Reagent B +C - put in refrigerator
- activation capsules - room temp
- VDK caps - room temp
Make sure all samples are treated the same. You should be filtering out yeast and make sure you are using the same filters. Make sure they are taking the same amount of time to filter. If you are centrifuging yeast out, make sure that is always done for the same amount of time between samples. Make sure samples are all the same temperature when you are running the tests. For example let any samples what may have been stored in the fridge warm up to room temp before running the assay.
Make sure your hot bath is at 70C. Use an external thermometer to double check any digital read outs. Make sure that the hot water baths' water line is above the sample's water line.
Only run 1 to 2 tests at a time.
Make sure you are mixing the Reagent A+B+C mixture well before adding it to the caps.
This is the order we add everything when we run a test:
- Add Activation Capsule to glass vial
- Mix Reagent A+B+C
- Measure out sample and set to side
- Add Reagent A+B+C to cap.
- Pour sample in to glass vial, place cap onto vial immediately on top.
- Place into hot bath for 15 minutes.
Try to keep the order and the time it takes to add everything the same.

How to use the VDK+ Test Strips?

2/12/2021

Download the white paper below to see how you can use the VDK+ Test Strips to improve your beer quality program!

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Why spend money on VDK+ Test Strips?

2/12/2021

Download the whitepaper below to see why VDK+ Test Strips could save you money!

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How to perform a VDK+ Test Strip Reaction (In-depth)

2/2/2021

Follow this video to learn how to perform a VDK+ Test Strip reaction.

What are vicinal diketones (VDK's) and why do they matter?

1/26/2021

2,3-butanedione (diacetyl) and 2,3-pentanedione, colloquially known as vicinal diketones (VDKs), are metabolic by-products of yeast fermentation that impart buttery flavor characteristics to fermented beverages. Although desired in certain cases, VDKs are frequently denoted as an off-flavor in finished beer, cider, kombucha, and wine when present at concentrations between 100-4000 parts per billion (ppb).

Organoleptic perception of VDKs varies greatly between people. For example, trained sensory experts can detect VDKs down to 40-100 ppb in beer depending on the style, while a substantive fraction of the population cannot discern VDKs present even at levels exceeding 4000 ppb. This range in sensory perception has led to the development of several chemical assays specific for VDKs in beer.

Current methods for monitoring VDKs generally utilize either gas chromatography paired with a specialized detector (e.g. GC-MS or GC-ECD) or distillation of a beer sample followed by colorimetric reaction and detection via spectrophotometry. Methods utilizing gas chromatography require expensive instrumentation, while methods utilizing spectrophotometry are technical and require large amounts of time for a single measurement. Both general workflows require sufficient chemical training. This is why we developed our proprietary VDK+ Test Strips.