What's in a wine?

My parents drink wine a couple of times during the week. This is not a tradition but a recent habit. Why? The answer to that question can be traced to my father's best friend Ali. Ali considers himself an expert on wine or a viticulturist. He may understand the general basics about wine but he lacks understanding of the chemical and biological components. Rumor has it that his pride has driven some people crazy! Haha. Hopefully, my recent visit to Barone Ricasoli may appease these troubled souls. My knowledge, along with the rest of the class, lies specifically with Chianti Classico wine. Characteristics of Chianti Classico are a minimum alcohol level of 12º, newly planted vineyards 4 years after planting, ruby red color, vinous odor, acidity of 4.5 ppt., violet scent, and 4 grams per liter sugar. Each bottle of wine must follow strict production guidelines and government regulations. Visiting Barone Ricasoli revealed to me the difficulty in producing wine.

One aspect of Chianti Classico wine that intrigued me the most was the processes involved to produce different colors of wine. Depending on the desired color, juice is squeezed out either before or after the process of fermentation. To produce white wine, the juice of each grape is squeezed out before fermentation because grape skins give off color during fermentation. Red wine requires crushed grapes to be fermented before the juice is pressed out. Interestingly, the shade of red color for each wine can be controlled by varying the amount of grape skin during fermentation. For example, pink wine involves minimal skin fermentation. Once fermentation is completed, the juice is quickly squeezed out so that a small amount of red color seeps into the collected product.

Further research revealed to me that the color of red wine is the result of anthocyanins in grape skin. This should ring a bell! Through high-performance liquid chromatography (HPLC), researchers were able to discover 5 different 3-monoglucosides in grape skin. HPLC uses retention time to identify molecules through molecular interactions with the chosen solvent.


Sources:
Rovner S. (2006, May 1). Vintage Chemistry. Retrieved June 15, 2009, from http://pubs.acs.org/cen/science/84/8418sci1.html
Vine R., Harkness E., & Linton S. Winemaking: From Grape Growing to Marketplace. New York: Springer.