produced are acetaldehydes, which adds the flavor necessary for the final product of tequila. For example, isovaleraldehyde seems to produce a sweet, cocoa, and chocolate-like flavor. 2 and 3-methylbutanal produce a malty flavor. The agave plant contains many phenolics such as vanillin and syringaldehydes which presents a strong and fruity or herbal aroma. It also contains eugenol which can deliver a hint of spicy flavor to the tequila. Since the production of tequila involves heating, Maillard browning reactions occur, and furans are produced during the thermal degradation of sugar. The most prominent furanic compounds include 2-furaldehyde and 5-methylfuraldehyde, which can contribute to the smoky flavor of tequila. Guaiacol also seems to contribute to Tequila's smoky flavor. Beta-demascenone contributes to the woody, floral taste of tequila. Volatile compounds that contribute to the overall taste and aroma of tequila can be quantitatively assessed and evaluated by gas chromatography. Discrimination tests such as duo-trio and triangle tests are also used to evaluate the quality of the tequila. Aging Process If silver or white (Blanco) tequila is the desired final product, distillation is the final process it undergoes. Rested (Reposado) or aged (Añejo) tequila must be matured in 200-liter (or larger) white oak barrels for at least two months for the former and 12 months for the latter. There are, however, more than 50 different companies producing tequila in the Mexican province of Jalisco, with different maturation times according to the variety of tequila and desired quality of the final product. All companies producing tequila have their aging processes regulated and fiscalized by the Mexican government. Chemistry The maturation process causes four main chemical transformations to the tequila compounds: (1) decreasing of fusel oils by the char in barrels, which acts as an absorbing agent; (2) extraction of complex wood constituents by tequila, giving specific aroma and flavor to the final product; (3) reactions among the components of tequila, creating new chemical compounds; and (4) oxidation of the original contents of tequila and of those extracted from wood. The final results of these changes are increased concentrations of acids, esters and aldehydes, and a decrease in fusel oil concentration. Reposado may be rested in oak barrels or casks as large as 20,000 liters (5,280 gallons), allowing for richer and more complex flavors. The preferred oak comes from the US, France, or Canada, and is usually white oak. Some companies char the wood to impart