The purpose of the experiment is to investigate the changes which occur when two different wines are left in half filled wine glasses exposed to air. The changes will be observed by visual inspection and by evaluating the aroma characteristics by smelling.
Introduction.
The wine's ability to matur/ age properly is dependent on both endogenic factors as well as exogenic. The endogenic factors are multifarious, but the two most important factors are acidity/ pH and tannin/ polyphenol content. These are not discussed further, since they are not investigated in the experiment.
The main exogenic factors affecting wine maturation/ aging are temperature, oxygen, light and mechanical action1. The rate of chemical reactions are dependent of temperature, as rule of thumb the rate will double for every 10 oC increase, so all other factors being equal, the many chemical reactions (oxidation, condensation, polymerization etc.) that can occur in wine, will speed up with increasing temperature. Light, especially UV light, can influence wine composition by catalysing reactions between polyphenols, anthocyanins etc., resulting in colour changes. Mechanical actions, like vibrations, can induce changes in the wine, for instance by impeding sedimentation and by mixing the wine, leading to increased chemical conversion.
Oxygen can cause changes in the wine in two ways. Oxygen can react direct with different molecules present in wine. Important are the polyphenols with vicinal 1,2-dihydroxy groups, which, when oxidized by oxygen, produce hydrogenperoxide, a very potent oxidizing agent,.
capable of oxidizing other molecules. Ethanol can be oxidized this way, leading to formation of acetaldehyde. The other way oxygen can impact the wine is by stimulating the aerobic micro organisms (like Acetobacter) eventually present in the wine, leading to predominantly unpleasant notes, like acetic acid .
This experiment, where a sample of wine is left exposed to air in a glass, is a simple way to simulate the changes that will occur if the wine during the maturation/ aging process is exposed to air (for instance by racking, filtration, pumping and air pockets due to ullage).