Technically Speaking: Aging

An excerpt from a research paper I submitted for my UC-Davis Wine Production class:

“Oxidation is a chemical process consisting of the interaction between oxygen molecules and various substances they may contact and is often considered a problem in winemaking such that considerable efforts are employed to prevent it throughout the wine making process.  On the other hand, oxygen exposure plays an important role in wine aging as some wines can benefit from extensive oxidation effects such as browning, which is desired in the production of Madeira, Port and Sherry but are not especially favored in white wines (Boulton et al. 1996), and creation of desired “oxidized flavors” as well as tannin softening and color stabilizationfrom limited oxygen exposure (Linda Bisson, 2008, Lecture Notes)(Waterhouse and Laurie 2006).  It was shown that in Sauvignon Blanc and Chardonnay wines fruitiness and overall quality decreased as exposure to oxygen increased, yet quality increased for Sherry (Singleton 1979).  Other off-characters produced by oxidation include “pinking” in white wines and the formation of aldehydes, mostly in the form of acetaldehyde which is a sure sign oxidation has taken place (Linda Bisson, 2008, Lecture Notes).  The primary reason red wines are more age-worthy than whites is due to the amount of phenols present which determine the wine’s capacity to consume oxygen and transform (Singleton 1987) and is the main “oxidizable substrate” in wine (Singleton et al. 1979).  It is important to note that there is a point in time in the life of the wine where it will no longer reap oxidative benefits and begin to reduce in quality(Boulton et al. 1996).”

Basically, many important aging reactions are oxidation-reductions, or redox, however there are other chemical reactions that are not dependent upon oxygen.  When someone refers to “bottle bouquet” they are (or should be) talking about components and characteristics that appear while aging in the bottle – think about that musky note you might get with some older French wines.  And in most cases, when we talk about aging, like in this recent post discussing the value of aged wines, we are talking mostly about bottle aging.  Sometimes the woody attributes you may get in a French wine may not be from oak after all, but rather bottle aging.  However, the winemaking topic of Aging also includes doing things in the winemaking process prior to bottling to help ensure stability or correct a particular defect in the wine, and we also know that there is extended barrel-aging for style as produced in Spain as well but that’s a topic of discussion for another time.

There are several variables to consider when aging: Time, Temperature, Oxygen, Cooperage (Barrels), pH (acid) and Chemical Composition of the wine.  The rate of chemical reactions increase with the increase in temperature.  This is why Bern’s in Tampakeeps their wine cellar colder than “normal” as it allows slower aging, therefore hopefully extending their life.  However, this doesn’t necessarily mean you impatient folks can speed up that aging process either just by cranking up the heat because it could cause the loss of certain desirable compounds or it could make certain components stronger than others which is not desirable.  This is why aging should be done between 7-24C (45-75F) though a more targeted range for your cellar is probably 55-58F for best results.

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Cheers!

Literature Cited

Bisson, Linda. 2008. Wine Production for Distance Learners Lecture Notes.

Boulton, R., V. Singleton, L. Bisson, and R. Kunkee. 1996. Principles and Practices of Winemaking. Chapman & Hall, New York.

Singleton, Vernon L. 1987. Oxygen with Phenols and Related Reactions in Musts, Wines, and Model Systems: Observations and Practical Implications.  Am. J. Enol. Vitic., 38: 69 – 77.

Singleton, V. L., Eugene Trousdale, and John Zaya. 1979. Oxidation of Wines. I. Young White Wines Periodically Exposed to Air. Am. J. Enol. Vitic., 30: 49 – 54.

Waterhouse, Andrew L. and V. Felipe Laurie. 2006. Oxidation of Wine Phenolics: A Critical Evaluation and Hypotheses. Am. J. Enol. Vitic., 57: 306 – 313.