Đăng ngày 23 May, 2021 bởi admin - chuyên mục Blog

Scientists have been promoting the benefits of eating fresh food in our daily diet. But the exceptions to this rule are the many wines that actually need some aging to taste their best. Winemakers know this and work to control the aging process including decisions they make about how to bottle up their product.

Aging and oxygen

One aspect of aging has to do with the reaction of fruit acids with alcohol. This process reduces sourness in the wine, but it’s really only important for very tart wines, the ones coming from cold climates.

The complex oxidation process is the second aspect of aging. When oxygen interacts with the wine, it produces many changes – ultimately yielding an oxidized wine that has a nutty aroma. This is a desired taste for sherry styles but quickly compromises the aromas in fresh white wines.

However, the oxidation process provides benefits along the way to that unwanted endpoint. Many wines develop undesirable aromas under anaerobic –no oxygen– conditions; a small amount of oxygen will eliminate those trace thiol compounds responsible for the aroma of rotten eggs or burnt rubber. Oxidation products also react with the red anthocyanin molecules from the grapes to create stable pigments in red wine.

The way a bottle is sealed will directly affect how much oxygen passes into the wine each year. That will directly affect the aging trajectory and determine when that wine will be at its “best”.

Stick a cork in it?

Glass is a hermetic material, meaning zero oxygen can pass through it. But all wine bottle closures admit at least a smidgen of oxygen. The actual amount is the key to a closure’s performance. A typical cork will let in about one milligram of oxygen per year. This sounds like a tiny bit, but after two or three years, the cumulative amount can be enough to break down the sulfites that winemakers add to protect the wine from oxidation.

 

Which sealing method is best?

The way a bottle is sealed will directly affect how much oxygen passes into the wine each year. That will directly affect the aging of the wine and determine when that wine will be at its “best.”

No oxygen can pass through glass, so it is considered a hermetic material. At the same time, all wine bottle closures admit at least a little bit of oxygen. The actual amount is the key to a closure’s performance. A typical cork will let in about one milligram of oxygen per year. This sounds like a tiny bit, but after two or three years, the cumulative amount can be enough to break down the sulfites that winemakers add to protect the wine from oxidation.

There are three major closure options available: natural cork (and technical cork, its low budget brother made of cork particles), the screw cap and synthetic corks.  

  1. Natural Corks
    Natural cork stoppers appeared about 250 years ago, displacing the oiled rags and wooden plugs that had previously been used to seal bottles. With the use of cork came the possibility of aging wine. Until about 20 years ago natural corks were pretty much the only option for quality wine. The cork cylinder is cut from the outside to the inside of the bark of the cork oak tree.
  2. Screwcaps
    Screwcaps are actually two parts: the metal cap and the liner inside the top of the cap that seals to the lip of the bottle. The liner is the critical part that controls the amount of oxygen getting into the wine. Back when screwcaps were only used on jug wine, there were just two types of liners available. But today multiple companies are jumping in to offer their take on what rate of oxygen transmission is best, as well as to replace the tin used in one of the traditional liners. The standard liners admit either a bit more or a bit less oxygen than good natural corks. Screwcaps, being manufactured, are also very consistent.
  3. Plastic Corks
    Synthetic corks are made from polyethylene, the same plastic as milk bottles and plastic pipes. After years of research and development, these corks perform nearly the same as the natural version with three exceptions: they have no taint, they let in a bit more oxygen and they are very consistent in oxygen transmission.
    Their consistency is a major selling point to winemakers because the wine will have a predictable taste at various points in time. In fact, winemakers can tweak the oxidation rate of their wine by choosing from a range of synthetic corks with different rates of known oxygen transmission.

 Is there an optimum wine closure?

Synthetic closures are cheaper, predictable and great for everyday wines.
Natural cork is the only cork proven for long-term aging.

The performance of the manufactured closures, made with 21st-century technology, is excellent. Generally, they approximate our expectations, based on over two centuries of experience aging with natural cork closures.

For the regular wine, you might purchase for dinner this weekend or keep for a year or two, any of these closures are perfectly good, while the manufactured closures avoid taint. In fact, your choice is more a matter of preference for opening the bottle. Do you want the convenience of twisting off the cap, or do you want the ceremony of removing the cork?
For long aging, however, the only closure with an adequately long track record is natural cork. So to be safe, that is the closure to choose. Once we have solid long-term evaluations of synthetics and screw caps, it will be possible to judge their suitability for extended aging, such as more than ten years.

Over centuries, winemakers have consistently taken advantage of new technology to improve their product, from oak barrels to bottles to modern crushing and pressing equipment and micro-oxygenation. While manufactured closures have some key advantages, it is proving difficult to displace natural cork due to its centuries-old tradition, albeit with a few problems, and its connection to the natural environment.

 

0 0 votes
Article Rating
Subscribe
Notify of
guest
0 Comments
Inline Feedbacks
View all comments