What Goes Inside the Wine Barrel: The Process of Aging In Oak

Many of us drink wine on a regular basis, but have you ever thought about the process that goes into making each bottle? Creating wine is an art and a science, and aging is an important part of the process. Aging softens the “burn” of the ethanol while smoothing out flavors and adding unique characteristics to the wine.

The choice of barrel, the fermentation process, the distillation technique and equipment will all have an effect on the overall chemical composition – the smell and taste – of the final product. Oak barrels are among the most popular vessels for aging because they’re durable, easy to shape, fairly inexpensive, and less reactive to their contents. Distillation affects the wine’s ethanol level, but also has an influence on aldehydes, esters and fatty acids. These elements all have very specific aromas and flavors, and the individualized combinations of each are what differentiate one wine from another.

Read on to discover some key factors that go into the process of aging wine in an oak barrel—each effecting the aroma and taste.


Time is unpredictable.  Just a few days could turn a good wine into a bad wine. Red wine is usually aged in a barrel for one to two years—sometimes longer— before bottling. White wine, however, is aged for a shorter period of time. For example, our 2014 Chardonnay was barreled for just less than 11 months.


Oxidation can have a positive or negative impact on the wine making process. When oxygen reacts with alcohol it creates acetic acid. If a wine is in a cellar for too many years this acetic acid can ruin the product. However, exposure to oxygen can be a positive when it comes to fruity wines. Aging a fruity wine for a longer period of time can add earthy and nutty flavors to its already fruit-focused profile.

Oxygen is extremely reactive, and with wood being porous, oak barrels allow only small amounts of air to pass in and out of the barrel. This controls the rate at which the congeners are oxidized. During this process, ethanol can oxidize or evaporate, causing the proof (alcohol-by-volume) to drop.

Tannins and other Phenolic Compounds

Phenolic compounds are the chemicals that are responsible for the tastes and smells we recognize in food. These change slowly in a bottle of wine as it ages. There are multiple kinds of phenolic compounds, but the most important of these is tannins.

Tannins love to bind to proteins – red wines are high in tannins, which is why they often go well with red meats. The puckering and astringent feeling you may experience while drinking wine is in due in part to tannins binding to the proteins in our saliva. Polymerization takes place when tannins are bound together in long chains, and once bound together, they fall to the bottom of the bottle as sediment. This process causes the wine to weaken in taste.


Wine is often considered to be a living, breathing organism, and we couldn’t agree more. Esters play a big role in the “life” of a wine by reacting to the different components and adding strong flavors as the wine ages.  Esters are a result of alcohol reacting to oxygen and acids, ultimately causing the tannins to lose their harshness. When tannins lose their bitterness, the aroma qualities are increased and the esters boost the wine’s flavor.

Categories: Winery, Winemaking