According to some studies, oak has five components that may influence the maturing drink. These components are cellulose, lignin, hemicellulose, oak tannins and naturally occurring preservatives compounds. Although cellulose has no effect on the drink, it will hold the oak wood together. When heated, the lignin will yield vanillin. Vanillin gives the beverage a sweet, smoky and spicy taste. The hemicellulose contains simple sugars. When heated, these sugars will break down to give the drink toast and caramelized flavor. The oak tannins will help in the maturation of the whiskey by enabling the oxidation process.



Whiskey makers only use three species of oak to store their products. These kinds of oaks are the Quercus Alba or White Oak, Quercus Petraea or Sessile Oak, and Quercus Robur or Pedunculate Oak. Quercus Alba is also referred to as American Oak. It is the most commonly used oak in whisky cooperage. The American Oak provides woody, coconut and vanilla flavors. Meanwhile Quercus Petraea is usually utilized for wine cooperage. It is found in Europe, specifically in France. This oak provides a more vanilla flavor. Quercus Robur is found in Europe. It provides prune and raisin-like flavors. It is commonly used for sherry and cognac cooperage.



Whiskey oak barrels are usually available in three sizes. The barrels size is about 190 liters or 50 gallons. The Butts size contains 500 liters or 132 galloons of whiskey. The Hogsheads size contains 250 liters or 66 gallons of the beverage. In general, the larger the barrel, the slower is the maturation of the whiskey. Smaller casks provides for quicker maturation because the whiskey is exposed to more wood area.