It is common to hear about oxidations and reductions while talking about wine production. These are two core factors when it comes to wine quality.
But, do we really know what we are talking about? Here’s what you need to know about oxidations and reductions in wine
Few boring chemistry notions
This may not be the reason why you are reading this post, but it’s worth to spend a few words on the chemistry behind these two reactions. First, oxidation consists of an increase of the “oxidation state” of a molecule due to another molecule, or it can be due to a loss of electrons.
While reduction is the opposite: reduction of the oxidation state of a molecule. This time due to an increase of electrons.
What is the cause of oxidations and reductions?
The answer is easy, oxygen. I mean the exposure of the wine to oxygen. We previously talked about how different corks, different wood cask, or amphoras can influence micro-oxygenation over time. But let’s break down which are the production phases leading to an oxidized or reduced wine.
Oxigen in wine production: best friend or worst enemy?
(1) The story starts with the grapes being harvested and brought into the cellar. If these soft grapes are broken the juice gets in contact with the oxygen starting the fort oxidation phase.
(2) But let’s move to the core of the vinification process. As you know lees need oxygen to begin the fermentation, therefore the must need to be oxygenated. How? Being pumped over the cap. This important and delicate phase can ruin the wine if it’s not executed properly, leading to an over oxygenation. Here comes a useful “tool” to wine producers: sulfites. These can avoid oxidations if added in large quantities to the wine. As you may know, I don’t like this practice at all and it’s very bad for our organism. It’s always better two pay extra care in the cellar during vinification rather than abusing chemical substances.
(3) The other vinification phase to consider is maceration. Here the wine is full of O2 making a sort of barrier against oxygen. For white wines, also the grape skins can help prevent oxidation, but when the maceration lasts too long and not controlled can lead to a reduction.
(4) After vinification we have the ageing. As we said, ageing can take place in different “containers”, these can be barriques, big wood cask, amphoras, fiberglass tanks, etc.
What’s the difference between these? Easy, the oxygen exchanges between the outside and the wine.
So, what happen to the wine in practical terms?
Let’s talk about oxidation first. When a wine keeps being in touch with oxygen, it will start changing color, becoming darker, and changing its taste. The latter is the worst scenario ever for a wine producer or wine collector. When the contact with oxygen is relatively long the wine starts to lose freshness becoming more and more acid. The classical flavor of oxidized wine is “marsala”; that’s why we say “vino marsalato”, lit. “marsala-like wine”. To give you an idea of its taste: a mix of vinegar, apple peels, and quince. Remember, this problem can happen anywhere in the four steps reported above.
What about reduction? Reduction is the opposite of oxidation: the wine didn’t spend enough time in contact with oxygen. Reduction can happen when the producer is trying to prevent oxidation too heavily and end up running the wine anyway.
This time, the smell remembers sulfur or cooked eggs! Reduction is harder to find in a wine, since it can only happen during the production phase and not afterward. Moreover, reduction can sometimes be resolved with a decanter or just waiting for the wine to evolve.
I hope you guys enjoyed this, it’s not a very fun topic but it’s extremely important to know this!
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