Digging into how and why wines age.
Have you ever wondered why some wines improve over time while others are best consumed young? The answer lies in the complex chemical reactions that take place as wine ages. In this post, we'll explore how wine ages, what factors influence the ageing process, and how different types of wine age differently.
Easy-drinking wines are designed to be consumed young, relying on their youthful vibrance and pronounced aromatic profile. On the other hand, more serious wines are built to age, with specific characteristics in their youth that aspire to complex over time and become better during their ageing process.
As the wine ages, it matures and evolves at different rates depending on its grape variety and origin. White wines that have been barrel fermented, such as Kershaw Chardonnay, have been exposed to micro-amounts of oxygen and are more stable than wine made anaerobically. Over time, barrel-fermented Chardonnay is able to withstand and notably complex as the wine ages. Barrel maturation for both red and white wines also enhances this ability.
Wines with a low pH are far more capable of evolving than those with a higher pH. Typically, cool climates such as Elgin give super-low pH's to Chardonnays and similarly lower pHs on the Pinots and Syrah compared to warmer climates. Wines that are unfined and unfiltered (such as the Kershaw wines) retain higher levels of phenolics, flavour compounds, and in particular, tannins, enabling more extended ageing.
Red wines contain colourless tannins, a low concentration of anthocyanins (the colour), pigmented tannins, and more complex colloids such as tannin-polysaccharides and tannin-proteins. As wine ages, reactions and aggregations take place, and these continue in the bottle. When the resulting polymers and particles reach a specific size, they precipitate dark-reddish brown sediment, leaving the wine progressively less astringent as some of the red/blue pigments and tannins have precipitated. This is also why the wine turns from reddish-blue to reddish-brown.
The impact of the wine on the nose and palate also evolves. Certain flavour precursors that were attached to glucose detach themselves through a process of hydrolysis and contribute individual flavour characteristics to the older wine. Other flavour compounds responsible for the primary aromas of the grape and secondary aromas from the fermentation itself are also interacting with each other and the phenolics.
An initial nose of the wine is thus steadily transformed into a bouquet of tertiary aromas, a much more subtle array and arrangement of flavours.
Esters form from combinations of the increasingly complex array of wine acids with alcohol. Continued esterification in the bottle produces another range of possible aromas, all the more unpredictable since the esters form at very different rates.
A host of factors influence the rate at which all these things happen, including storage conditions (mainly temperature as discussed above), the state of the cork or other stopper, the ullage of the wine at bottling, its pH level, and sulfur dioxide concentration, both of which can inhibit or slow the all-important influence of oxygen.
For white wines, apart from the pH, there is less real concrete evidence on how white wine ages. Research has shown that glycosides (and the hydrolysis of these constituents) help with the development of varietal aroma.
In conclusion, the ageing process of wine is a complex and fascinating phenomenon that involves various chemical reactions and interactions. The ageing potential of a wine depends on several factors such as grape variety, origin, pH level, tannin structure, and storage conditions. As the wine ages, it develops complex and subtle flavours and aromas, transforming from its initial youthful vibrance to a more sophisticated bouquet of tertiary aromas. While much is still unknown about how white wines age, research has shown that glycosides play a crucial role in developing varietal aroma. Ultimately, the ageing potential of a wine is a delicate balance between the wine's intrinsic characteristics and the conditions under which it is stored, making each bottle a unique and exciting experience.
Colloids: any substance consisting of particles substantially larger than atoms or ordinary molecules but too small to be visible to the unaided eye.
Tannin: these are a class of naturally occurring compounds found in plants, known for their ability to bind and precipitate proteins
Polysaccharides: complex carbohydrates made up of long chains of sugar molecules.
Tannin polysaccharides: complex molecules that are formed by the combination of tannins and polysaccharides. They are primarily responsible for the stability and mouthfeel of a wine.
Tannin proteins: complex molecular compounds formed by the binding of tannins and proteins. They are primarily responsible for the astringency and mouthfeel of red wines.
Glucose: one of the two main types of sugar found in wine.
Hydrolysis: a chemical reaction that involves breaking down a molecule into smaller units through the addition of water. A water molecule splits into a hydrogen ion and a hydroxide ion and these ions are used to break the chemical bonds between atoms in a larger molecule.
Esters: a type of organic compound formed from the reaction of a carboxylic acid and an alcohol. In wine, they are aromatic compounds formed during fermentation.