Like human beings, a wine’s taste is going to depend
a great deal on its origins and its upbringing.
- Linda Johnson-Bell, Pairing Wine & Food 

Here in wine production we have one chance, during harvest, to make great wine. We have many chances after that, to take great wine and mess it up.  One of the easiest ways to do that is through neglect. This week we are topping up our wine barrels and I thought I would talk about the importance of this process.

During the course of aging in barrels, wine evaporates through the barrel staves. The evaporated wine we affectionately name the “angels share”. This evaporation leaves a space in the barrel called head space which increases the wines contact with oxygen.

Oxygen in wine is a fickle friend; it makes our wines more supple and less astringent. It also makes the color in the wine more stable and of a richer hue. However, it oxygen invites wild yeasts, molds and bacteria to multiply and be merry which can lead to some organic chemistry interactions that produce acetaldehyde and other reactions that can turn the rich hue of wine from ruby or garnet to tawny or the extreme of brown.

Some of the usual suspects of yeast and bacteria growing in wines are; Acetobacter, Film Yeasts, and Lactic Acid Bacteria.  Acetobacter is an Obligate Aerobe.  This means that it requires oxygen to grow.  Its growth leads to an increase of acetic acid and other volatile acids as it converts ethyl alcohol to acetic acid.

Film yeasts are another group of micro-organisms that require oxygen to thrive in wine. There are a number of yeasts that make up this group and there is a characteristic white film that forms on top of the wine.  These yeasts also produced acetaldehyde as part of their growth process. Acetaldehyde is responsible for the nutty sherry aroma in Sherries and gives the same smell to oxidized wines.

One of the most effective ways, besides topping the barrels, to control both oxidation and spoilage organism is to add sulfur dioxide to the wines.  It is added to the wine during topping when it is needed.  Sulfur dioxide is produced naturally by yeasts via amino acid metabolism; however, not in enough volumes to protect the wines.  So we bolster this protection with more sulfur dioxide in accordance to its pH.  The amount of sulfur that is free to bind oxygen and inhibit spoilage organisms is dependent on the acidity of the wine.  The higher the acidity the less sulfur dioxide is needed to actively protect.

We protect these wines from the time we get the grapes in the door, until we put the finished wine in a bottle.  From our cellar to your table, please enjoy.