Woods for aging
Various woods impart different flavors to spirits as they age. The structure of the wood also affects the Angel's Share and oxidation of the spirit. Distillers select from the various woods, time, Char Level, and Toast Level to develop a flavor profile all their own. 60-70% of the flavor of a spirit will come from the wood used to age it.
As always, Safety first. When selecting a non-traditional wood you must understand if the wood is safe. Sumac is a very common tree in America but the sap of which is toxic. If you can't confirm it is safe don't use it.
Barrel or Inserts
Another aspect of using wood for aging is if the wood is going to be used as a container or as an insert to a second container. If the wood is to be used as a container the Angel's share is a consideration. As an insert this isn't a concern.
Significant Aspects of Wood
- No flavor contribution, but is the structure of the wood. Important when using the wood as a container.
- Simple sugars that break down when heated and provide body through the addition of wood sugars. When heated provide color, toasty & caramelized flavors/aromas through the Maillard Reaction and caramelization.
- The binding agent that hold the cellulose in wood together which, when heated yields vanillin, sweet, smoky and spice aromas
- Which play an essential role in maturation by enabling oxidation and the creation of delicate fragrance in spirits. Tannins combine with oxygen and other compounds in the spirit to form acetals over time. Tannins are naturally occurring preservative compounds with a slightly puckery, astringent taste in the mouth, similar to the effect of strong black tea or fresh walnuts. When someone says something is over-oaked, they are normally referring to tannins being too strong. A strong astringent taste is the easiest to detect.
- Resulting from lipids in the Oak, they increase dramatically during toasting and charring and can pass on a strong woody and perhaps coconut character; lactones give bourbon its distinctive character; and occur in higher concentrations in American Oak than in European varieties.
Commonly Used Woods
- White oak (Quercus Alba), America. Commonly referred to as “American Oak” and is the most commonly used variety in whisky cooperage. More vanillin than European varieties. Fast growth High in lactones, which when toasted, provide woody, vanilla, and coconut flavors
- Quercus Petraea, Europe. Found across Europe, notably in France. Most commonly used for wine cooperage. Slow growth, fine tannins and more vanilla (compared to Pedunculate). Most common species in Tronçais forest.
- Quercus Robur, Europe. Found across Europe. AKA English Oak, French Oak, Hungarian Oak. Noted for spiciness and the dried fruits. It is very porous as a species and slower growing than its American counterpart. The porous nature (increasing the Angel's share) and the slow growth of this species has cause it to go out of favor to the White Oak.
- Quercus falcata, Eurpose. Generates more raisin, prune-like flavors.Most commonly used for cognac and sherry cooperage. Fast growth, more tannins, thus more oxidative characteristics in the matured products (compared to Sessile).
- Quercus mongolica, Japan. The wood has extremely high levels of vanillins but is soft and very porous, making the casks made from mizunara oak very prone to leaking and easily damaged. As a result, the practice of maturing whisky was modified in order to reduce these factors. Now most Japanese whisky is matured in either bourbon or sherry casks and then transferred to mizunara casks to gain its flavorsome characteristics.