Experimental wine bottle tracks oxygen moving through the cork
Experimental wine bottle tracks oxygen moving through the cork
实验性酒瓶追踪氧气穿过软木塞的过程
Most people perceive a cork in a bottle of wine as a simple plug meant to keep the liquid in and the outside world out. In the recent study published in Science Advances, a team of French scientists demonstrated the cork is way more than that. By regulating the oxygen transfer into and out of the wine bottle, it works almost as another ingredient. 大多数人认为葡萄酒瓶上的软木塞只是一个简单的塞子，用来防止液体流出并隔绝外界。在最近发表于《科学进展》（Science Advances）的一项研究中，法国科学家团队证明了软木塞的作用远不止于此。通过调节进出酒瓶的氧气传输，它几乎起到了另一种“配料”的作用。
“Twenty years ago, our group focused on the oxidation and aging of wine and all its parameters,” Thomas Karbowiak said. “Oxygen diffusion through cork stoppers is one of these parameters.” Karbowiak is a chemist at the University of Burgundy, France, and the senior author of the study. “二十年前，我们团队专注于葡萄酒的氧化、陈年及其所有相关参数，”托马斯·卡尔博维亚克（Thomas Karbowiak）说，“氧气通过软木塞的扩散就是其中之一。”卡尔博维亚克是法国勃艮第大学的化学家，也是该研究的资深作者。
The mini-bottle experiment
微型酒瓶实验
Oxidation is one of the key drivers of wine aging. A slow, limited ingress of oxygen helps wine mature, smoothing out harsh tannins and bringing out an aromatic complexity. But when too much oxygen gets into the bottle too quickly, it can make the wine stale, brownish in color, and unpleasant to drink. That’s because it will also react with alcohol and phenols in the same process that makes a cut apple turn brown. 氧化是葡萄酒陈年的关键驱动因素之一。缓慢且有限的氧气进入有助于葡萄酒成熟，平滑苦涩的单宁并带来复杂的香气。但如果过多的氧气过快进入瓶中，会使葡萄酒变质、颜色变褐，口感变差。这是因为它会与酒精和酚类物质发生反应，过程与切开的苹果变褐原理相同。
The problem with trying to study this is that, in a standard 750 ml wine bottle, the volume of liquid and the thickness of the glass make it difficult to accurately isolate, monitor, and measure real-time oxygen kinetics without introducing external air or disrupting the internal environment. 研究这一问题的难点在于，在标准的750毫升葡萄酒瓶中，液体的体积和玻璃的厚度使得在不引入外部空气或干扰内部环境的情况下，难以准确分离、监测和测量实时的氧气动力学。
“The real bottle of wine is a complex system. We wanted something simpler and easier to understand,” said Julie Chanut, a researcher at the University of Burgundy and lead author of the study. To bypass this issue, the team designed a custom experimental rig they called the miniature bottle system. “The idea was to see what mechanisms are at work in this system,” Chanut said. “真正的葡萄酒瓶是一个复杂的系统。我们想要一种更简单、更容易理解的东西，”勃艮第大学研究员、该研究的第一作者朱莉·沙努（Julie Chanut）说。为了绕过这个问题，团队设计了一种定制的实验装置，他们称之为“微型瓶系统”。“我们的想法是观察这个系统中到底有哪些机制在起作用，”沙努说。
The setup consisted of small glass vials designed to mimic the standard cylindrical geometry of a commercial wine bottleneck. Each vial was sealed using scaled-down cork stoppers ranging in length from 6 to 42 millimeters; the interior could be precisely loaded with either gas or a specific volume of model wine. The reduction in the total volume of both the liquid and gas phases artificially amplified any oxygen concentration changes that occurred. 该装置由小型玻璃瓶组成，旨在模拟商业葡萄酒瓶颈的标准圆柱几何形状。每个小瓶使用长度在6到42毫米之间的缩小版软木塞密封；内部可以精确装入气体或特定体积的模拟葡萄酒。液体和气体总量的减少，人为地放大了氧气浓度的任何变化。
The system acted as a chemical magnifying glass that enabled the scientists to precisely measure extremely subtle physical and chemical mechanisms like outgassing through the cork or the reactions at the interface between the cork and the wine. Armed with their miniature bottle setup, the team loaded half of the vials with wine, left the other half empty, sealed them with the selection of different length corks, filled them with sensors, and left them for 18 months to age. It turned out the oxygen dynamics in the vials was way more complex than a simple, steady leak through the cork. 该系统就像一个化学放大镜，使科学家能够精确测量极其细微的物理和化学机制，例如通过软木塞的排气，或软木塞与葡萄酒界面处的反应。利用这套微型瓶装置，团队在半数小瓶中装入葡萄酒，其余半数留空，用不同长度的软木塞密封，装上传感器，并放置18个月进行陈化。结果发现，小瓶中的氧气动力学远比通过软木塞的简单、稳定泄漏要复杂得多。
Four phases of breathing
呼吸的四个阶段
During the experiment, the researchers learned there are four stages of oxygen transfer through the cork, which starts the moment a cork is rammed into a bottleneck. The first phase lasted for the initial 15 days after the vials were corked. “It was an equilibration between the liquid phase of the model wine and the gas phase,” Chanut said. 在实验过程中，研究人员了解到氧气通过软木塞的传输分为四个阶段，从软木塞被塞入瓶颈的那一刻开始。第一阶段持续在封瓶后的最初15天。“这是模拟葡萄酒的液相与气相之间的平衡过程，”沙努说。
There are differences in the gas content between wine that had been aged in sealed containers and the small bit of air that gets trapped and pressurized by the insertion of the cork. In the experiment, the oxygen dissolved in the liquid phase in the vials escaped back to the gas phase. 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. 在密封容器中陈化的葡萄酒与因插入软木塞而被困住并加压的少量空气之间，气体含量存在差异。在实验中，溶解在小瓶液相中的氧气逃逸回气相。然而，随后的第二阶段情况则更令人惊讶。沙努的团队观察到，在前六个月里，进入葡萄酒的大部分氧气并非来自外部环境。事实证明，氧气来自软木塞本身，从软木塞细胞结构的微小空间中扩散出来。软木塞实际上是在向瓶内排气。
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. 这也是研究人员发现样本间首次出现差异的地方——使用较长软木塞密封的小瓶获得了更多的氧气，因为较大的软木塞比短的含有更多的氧气。当软木塞开始与葡萄酒发生化学相互作用时（实验进行到大约四个月时），它就不再仅仅是一个密封件，而成为了一种“配料”。
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 outgassed 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. 在模拟葡萄酒与软木塞接触的小瓶中，液体开始充当溶剂，从软木塞中提取酚类化合物。这些化合物包括没食子酸、鞣花酸和原儿茶酸，它们都开始渗入葡萄酒中。一旦进入酒中，它们就充当了化学清除剂，在铁和铜等微量金属的催化下，与软木塞释放出的氧气发生反应。这一过程导致葡萄酒的氧含量明显下降——软木塞实际上是在部署化学物质来消耗它之前释放的氧气。
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. 最终，在15个月后，葡萄酒进入了第四个长期阶段。在此阶段，来自外部环境的氧气稳定而缓慢地渗透过软木塞。在第18个月实验结束时，研究团队注意到，在使用较长软木塞（超过30毫米）密封的小瓶中，最后阶段的氧气传输速率极低，以至于变化几乎无法察觉。
“Because we used model wine in the experiment and focused on oxygen transfer, we didn’t do any tasting tests,” Karbowiak said. But oxygenation does matter for taste and, Karbowiak claims, the team is already getting a lot of interest from both wine makers and cork manufacturers. “因为我们在实验中使用的是模拟葡萄酒，且重点在于氧气传输，所以我们没有进行任何品尝测试，”卡尔博维亚克说。但氧化确实对口感有影响，卡尔博维亚克声称，该团队已经引起了酿酒商和软木塞制造商的极大兴趣。