"Thanks to an exclusive patented process for 'de-aromatising' cork, the 'Diam' and 'Mytik Diam' corks are the only cork closures that are completely neutral in sensory terms," the manufacturer promises, guaranteeing "the preservation of the wine's aromas throughout its storage period" as well as "consistently impeccable enjoyment". For this, the cork granulate is treated with the "Diamant®process" technology. According to the company, it uses "the possibilities of supercritical CO2", with which "the volatile and harmful substances are to be extracted, thus eliminating the risks of TCA
'cork taint'". Renowned companies such as Champagne
and Billecart Salmon, Louis Jadot
from Burgundy, Hugel et Fils
in Alsace and the renowned French
wine consultant Michel Rolland
use and promote Diam
corks. However, wine merchant Rolf Cordes from Mühldorf in Bavaria has doubts about the company's promise. He claims that Diam
corks produce an "atypical bitter
tone". He has found this out after many years of tasting wines from all over Europe. To prove his thesis, he recently organised his own sensory investigation and now wants to publish the results online. Wein-Plus
asked him about his accusations, findings and evidence.
Mr Cordes, you say that the agglomerated corks of the French
supplier Diam Bouchage
, which are used billions of times worldwide, could negatively change the taste of the wines sealed with them. What makes you think that?
When tasting red, rosé
and white wines from different regions and grape varieties, I discovered taste parallels of a negative nature. I set out to find the cause. The only thing that all the wines had in common was the closure - the Diam
According to your observations, could corks from similar production processes of other manufacturers also be affected?
Basically, the conventional agglomerated corks are not considered sensory neutral. I notice this again and again, regardless of the manufacturer. However, the sensory changes of those corks are different and not as uniform as with the Diam
In your opinion, what defect do these corks cause? How can it be described?
I call the defect an "atypical bitter
tone", UTB for short. It causes an extraordinary dryness primarily in the pharynx, uvula and oesophagus. This astringency lasts longer than with the usual tannins, which are primarily felt in the mouth and palate. Under increasing influence of the air, a clear disharmony becomes noticeable.
When did the fault first
consciously occur for you? With which wines?
It's impossible to say. It's like a jigsaw puzzle. When the picture is finished, you no longer know which piece you started with.
Are you sure that only Diam
corks are affected?
Up to now, I have not noticed this missing tone in this way in any other agglomerated corks. The uniqueness was also confirmed to me by the experienced oenologist Volker Schneider
. He ran an independent wine analysis
laboratory for many years.
is subjective. Can you prove the contamination by the cork?
Yes. I selected eight different wines. For each wine, half of its quantity was brought into contact with a Diam
cork. I used two different procedures: On the one hand, three wines were bottled, two bottles per variety were screw-capped and sealed with Diam
. In addition, we filled five wines, which were screw-capped, into brand-new 1.5l glass containers. For each wine, there was one glass container without a cork and one that contained two diam
corks. The wines in the glass containers were gassed with argon to prevent oxidation
. The three bottled wines in group 1 remained in contact with the diam
corks for 37 to 94 days. The five wines in group 2 had a contact time of 32 to 72 hours, a maximum of three days. The wines were then bottled in coded 100ml bottles and sent to the tasters.
Who were the tasters?
They were wine journalist Jens Priewe
, oenologist Volker Schneider
, master winemaker and DLG
tester Lukas Schmidt
, winemaker and LWK tester Daniel Theisen, plus experts from wine control, quality wine testing and analytics as well as winemakers, wine merchants and end consumers.
What was the result?
The test proves that Diam
corks are not sensorially neutral. Due to the identical manufacturing process, it is irrelevant which Diam
type is used.
|Copyright: Rolf Cordes
How high was the recognition rate of the testers involved?
The off-flavour was recognised between 81 and 100 per cent
in seven wines and 72 per cent
in one wine.
Why did you decide on this test procedure? Did you develop it on your own?
A sensory test corresponded exactly to my requirements. The aim was to prove the effect on the wine and not to find the causative substance. I was advised in setting up the test by Volker Schneider
, an oenologist with a great deal of experience in research, sensory analysis
Some oenologists, however, say that the experimental set-up would probably change every wine with an off-flavour - no matter which closure you use. What is your opinion on this?
There were three wines which were corked
and five wines which came into contact with a Diam
cork in a glass container. The second method is generally used in research to control the transfer of substances into a solution, for example in the TCA
testing of natural corks. The assertion that any closure is likely to alter a wine with an off-flavour is expressed very sweepingly and is not tenable as such. However, if any other closure were to cause an off-flavour under these conditions, I believe it would have to be tested just as rigorously and carefully as Diam
was in this case.
cork promises the complete exclusion of TCA
, i.e. corkton. That is why it has been used worldwide for many years. Why has the fault you observed not been noticed by any winemaker, merchant or oenologist so far?
The basic prerequisite for coming across this off-flavour is to recognise it in the first
place. Perhaps they have already noticed something out of the ordinary, but could not attribute it to the closure. If you search for TCA
, you will not find the UTB. When testing, it is necessary to swallow some wine, otherwise the essential areas in the mouth will not be wetted. Since there is often no comparison with uncontaminated wine, the influence of Diam
remains undetected. In general, these sensations are often attributed to acidity, tannins, grape variety, climate
, soil and stage of development. The developing disharmony requires continuous observation, which is not possible during quality controls and wine events due to time constraints.
What do you want to achieve with your results?
The risk for winegrowers
and traders should be reduced. Faulty and disharmonious wines are not conducive to business, quite the opposite. The wine drinkers, i.e. the customers, have a right to wines that are not affected by closures. I am of the opinion that the producer Diam Bouchage
must urgently tackle the identification and elimination of the causative substance.
Have you contacted Diam
What are your next steps?
Now it is a question of making these results available to as many winegrowers
, oenologists and traders as possible. For this purpose, I have had them translated into five languages. Every trader, wine drinker can download the tests as a PDF at www.diam-test.info
and forward them to his vintners at home and abroad. Of course, I will continue to observe the development in the field of closures.