Wine is considered one of the alcoholic beverages that requires careful attention when it comes to preservation.
As proof of this, the sheer variety of stoppers available for preserving opened wine is beyond comparison with other types of alcohol.
Why is wine so delicate...?
One of the reasons lies in "oxidation."
Here, we explain wine oxidation based on Dr. Ronald Jackson's report, "WHYNOT and Wine Oxidation."
Please use this as a reference for preserving wine well.
About Wine Oxidation
When wine comes into contact with oxygen in the air, it easily triggers various chemical reactions.
For example, unless it is a wine slowly aged in oak barrels or a special style of wine, winemakers pour their heart and soul into thoroughly protecting wine from oxygen. (Especially fresh & fruity white wines!)
Not to mention wine during the vinification process, even commercially sold wines will inevitably be affected by oxygen once uncorked.
Here, we first summarize the effects of wine oxidation.
- What Happens When Wine Oxidizes
- Loss of Aromas
- What Changes Occur in the Wine?
Let us examine each of these in turn.
What Happens When Wine Oxidizes
When a bottle of wine is opened, approximately 14 ml of air flows inside. (Of which about 3 ml is oxygen.)
At this point, oxygen reacts with various phenolic compounds contained in the wine, triggering a variety of chemical reactions.
Let us look step by step at what happens to wine through these oxidation processes.
Wine contacts oxygen
↓
Oxygen reacts with phenolic compounds
↓
Oxidized phenols produce hydrogen peroxide
↓
Hydrogen peroxide reacts with organic components of wine
↓
Acetaldehyde and water are formed
↓
Browning of the wine and loss of fruitiness
↓
Turns into a sherry-like flavor...
Looking at this, one can understand that oxygen itself does not necessarily exert a direct impact on the wine, but rather it is "the result of various reactions caused by oxidation."
Many people must have had the experience where, after leaving an opened clear white wine alone, it turned brown and took on an indescribable flavor...
Let us remember this sequence first as the basics of the relationship between wine and oxidation.
Loss of Aromas
Looking at the wine oxidation described above, one can understand that acetaldehyde is a factor causing the deterioration of wine.
However, acetaldehyde readily reacts with sulfites and phenolic compounds contained in wine to form odorless compounds, so slight oxidation should not cause that much deterioration. (In other words, red wine is more resistant to oxidation. This is one of the reasons why handling natural white wine is difficult.)
Meanwhile, according to recent research, the decomposition by oxygen of components that strongly influence wine aromas, such as acetate esters and terpineols, is considered problematic.
In other words, for some young white wines whose appeal lies in their fruitiness, their aromas are rapidly lost through oxidation... That is what happens.
Furthermore, it was also found that even in red wine, aromas are lost due to the decomposition of components related to fragrance, although not as significantly as in white wine.
What Changes Occur in the Taste?
What kinds of changes occur in the taste of wine due to oxidation?
First, when there are effects caused by acetaldehyde-related sherry-like notes or browning, it is considered that the flavor becomes far removed from the original taste of the wine.
Even if this could be prevented with phenolic compounds or sulfites, the loss of the wine's inherent fruitiness cannot be avoided.
In young wines, fruity or floral aromas disappear, and in aged wines, the mature aromas are said to manifest in the form of off-odors.
If hit by this double punch, one can even consider that the wine has effectively become a different beverage from what was originally bottled...
How Can Wine Oxidation Be Prevented?
Once uncorked, wine cannot escape the effects of oxidation unless quite specialized wine stoppers are used.
As mentioned earlier, air (along with the oxygen it contains) enters the bottle after uncorking.
Even if it is recorked afterward, although a certain amount of air is pushed out of the bottle, turbulence occurs and oxygen remains in the headspace, so the oxidation reaction of the wine continues to progress.
So, what should you do?
First, there is the method of suppressing the amount of oxygen absorption into the wine as much as possible.
Since lower wine temperatures and lower pH values are said to suppress oxygen absorption, try to uncork in a location with as low a temperature as possible. (Whether the pH value is low or not depends on the wine...)
Also, naturally, reseal immediately with a cork or a wine stopper once opened.
This is because the longer it takes, the more the contact between wine and oxygen naturally increases.
However, once opened, wine will inevitably oxidize.
If you wish to prevent it at all costs, there is no choice but to use special wine stoppers or devices specifically designed to prevent oxidation.
That said, nitrogen gas injection types are reported to be more promising in terms of effectiveness than vacuum types or inert gas spray bottle types.
While nitrogen gas injection types are difficult for beginners to use, it may be worth giving them a try if you want to enjoy your precious wine deliciously.
Engaging Well with Wine
Wine is sometimes referred to as a living thing, and once you understand the reactions involved in oxidation, you should be able to see why.
This might have sounded like a negative impression, but of course wine does not become undrinkable the moment it is opened; we share this in the sense that its characteristics are lost when exposed to air for hours or extended periods.
For aged red wines or reductive white wines, a slight degree of oxidation may even steer things in a positive direction.
Engage well with wine.
Please take a moment to reflect on this again.
References
WHYNOT and Wine Oxidation
http://ftechjapan.jp/about/pdf/dr_ron.pdf