The second phase that followed, though, was where things got a little more surprising. Chanut’s team observed that, during the first six months, the majority of oxygen that was getting into the wine wasn’t coming from the outside environment. The oxygen, it turned out, was coming from the cork itself, diffusing out of the microscopic spaces in the cork’s cellular structure. The cork was basically outgassing into the bottle.
Credit:
Chanut, et al.
This was also where the researchers found the first differences between their samples—vials sealed with longer corks were getting more oxygen because the bigger corks contained more oxygen than the short ones.
The moment the cork became an ingredient rather than just a seal came around four months into the experiment, when it began to chemically interact with the wine.
In the vials where the model wine was left in contact with the cork, the liquid began to act as a solvent, extracting phenolic compounds from the cork. These compounds included gallic acid, ellagic acid, and protocatechuic acid, all of which started bleeding into the wine. Once there, they acted as chemical scavengers that, catalyzed by trace metals like iron and copper, reacted with the oxygen released from the outgassing cork. The process caused a noticeable decrease in the wine’s oxygen content—the cork was effectively deploying chemicals that consumed the oxygen it had previously released.
Eventually, after 15 months, the wine settled into the fourth, long-haul phase. Here, oxygen from the outside environment steadily and slowly permeated through the cork. In the 18th month, at the end of the experiment, the team noted that in vials sealed with longer corks (above 30 millimeters), the rate of oxygen transfer during this last phase was so low that the change was barely noticeable.
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