Exposing your spirits to oak imparts structure, complexity, additional sensory elements and of course new and exciting flavors. While oak adds many different elements to spirits and wine (a study published in May, 2005 identified more than 70 volatile aroma and flavor compounds) many of the recognizable aromas and flavors are identified with vanilla, spice, sweet, spicy and “woody” characteristics. Breaking it down a bit we can group oak into its basic aroma and flavor and composition.
CIS and Trans Oak Lactones are characters imparted by the un-toasted oak (yes, even though the wood is toasted on the surface there is still the soft white-oak underbelly lurking below the toast) Trans Oak Lactones impart a woody, earthy almost chocolaty aroma and some flavor characters, while the more intense Cis Oak Lactones impart more of a coconut floral aroma and some small taste. If you’ve ever chopped down an oak tree you’ll recognize these aromas very distinctly.
Furfural and 5-Methylfurfural contribute wood sugars and in turn body. As the oak is seasoned (exposed to air) those natural polymers begin to breakdown into simple sugars. When oak is exposed to higher temperatures (about 300 degrees F) during the process of toasting, more simple sugars are formed. These sugars become caramelized and caramel, butterscotch and mocha like aromas emerge. Smokey, toasty characters develop as the oak passes 420 F.
Vanillin and lignin As lignin is degraded by heat it releases vanillins, which are a group of spirit and wine complimentary chemical compounds. Predominately, vanillin (yup, that’s that nice vanilla like flavor) is released during oak lignin breakdown. During the seasoning process, lignin is broken down by the sun, rain, and various microflora. The process of breaking down the lignins is also speeded up by the heat applied during the barrel toasting process. In the wine industry there has been extensive time and research devoted to the scientific analysis of this process in order to impart more and richer flavor attributes.
Eugenol and Isoeugenol are related to both raw oak (eugenol) and the degradation of lignin by heat (isoeugenol). Another reduction of the lignins by heat leads to spicy flavors apparent in the aroma and the flavor. Once toasted the Isoeugenol imparts a clove flavor and aroma. Guaiacol and 4-Methylguaiacol impart a smoky, charred character as part of the process of the pyrolysis of the lignins in the oak. As the oak is more toasted the smokier, and more charred the flavor becomes.
Cellulose and Hemicellulose are natural polymers, and comprise about half of the total solids in white oak. Cellulose provides the structural integrity of the wood and participates only minimally in the actual influence on the character of the wine during aging in the barrel. That’s a good thing because you don’t want your chips, cubes, staves, etc. falling apart and dissolving into your spirit. Hemicellulose contributes significant vanillin during the breakdown of lignin as described above in the Vanillin and Lignin section. As the wood is heated the action on the hemicellulose forms wood sugars which contribute sweetness and caramelized flavors. As the heat rises and persists toasted flavors are released.
Tannins comprise about 1% of American oak and 8% of French oak. Tannins also are a key player in the aging process. Tannins live in the radial rays of oak trees and are governed by seasoning, stave shaping, toasting times and temperatures (tannins are heat sensitive and undergo cellular lysis when exposed to water.
What kinds of oak can I use in my drinks?
There are several species and sub-species of oak that are used in cooperage and oak alternatives around the world, but for those of us in the fermented hooch making world there are four Genus and species generally used for cooperage and oak aging. The species most widely in use are: the American oak, Quercus alba, and three European species, Q. robur, Q. petraea and Q. sessilis (the latter of which is arguably the most sought after oak for aging and cooperage).
For the home spirit and wine makers there are generally three types of oak available at many Local Home Brew Stores (LHBS), they are: American, French and Eastern European (mostly Hungarian-ish oak). Because barrels are expensive, and the footprint for storage is considerable, most home spirit makers use oak chips, cubes, dominos, and staves.
American oak imparts infuses more quickly and imparts more vanilla, woody, sugary, and toasty characters than it’s European cousins and is used mainly in red wines but is growing in popularity with all spirit makers because it tends to be less expensive, in- stock at the LHBS, and available in a wider range of toast levels. American oak is harvested from several locations including Missouri, Minnesota, Oregon, Virginia and Pennsylvania.
Eastern European oak (including oak trees from Hungary, Slovenia, Slovakia, Croatia, Lithuania, Russia, Romania, and Ukraine) is more expensive than American oak but less expensive than French oak.
Eastern European oak imparts it’s flavor more slowly than American or French Oak. Hungarian Oak is much less intense than American or French oak because the trees grow more slowly and are smaller, creating fine grain which in turn lends itself to very subtle extraction. The hemicellulose in Eastern European oak breaks down more easily, and imparts a unique array of toasted, vanilla, spicy, woody, sugary and caramel-like flavors.
French oak is more expensive than American and Hungarian oak. It also sports the highest tannin content of the various oak types used for cooperage, chips, cubes, dominos, staves, etc. French oak is more porous than the American and Hungarian types so it presents more types of extracts for spirits and wine. Since there are more extractives such as caryophyllene (sweet, woody, spice, clove and dry flavors) and copaene (dry and spicy kind of flavors)
French oak is highly prized for barrels and aging because of the number of complex characters it adds to the wine. It extracts more quickly than most other oak types, and can quickly overpower spirit if not monitored closely. French oak is found in several forests including: Nevers, Troncais, Limousin, Allier, Centre, Vosges, Bertrange and Jupilles located mostly in central and eastern France.
So how do I get the wood into the drink? The most cost effective and practical method for infusing the oak characters into your drink are oak chips and oak cubes. Oak for spirit and wine comes in a variety of shapes and sizes for many different fermentation, aging and storage vessels. For the home spirit maker oak chips and oak cubes are the most common form available at your friendly neighborhood LHBS. Oak chips and cubes come in a variety of toast levels and are generally comprised of American, French and Hungarian oak. The toast levels generally include, light toast, medium toast, medium plus toast (also called house toast by many retailers) and heavy toast. There are other variations offered by different manufacturers of oak chips and cubes, but for the most part you’ll find one of the toast levels mentioned above. Layering oak additions in phases is also a common practice in both wine and spirit production (that is start with a heavy toast, next a medium toast, next a mix of light and medium toast).
If you’re adding wood to a wine or spirit that has already dropped clear they recommend rinsing the oak cubes off with some warm distilled water to remove the wood dust (sawdust) that is produced by the cubes rubbing together in the packaging. Make sure you use distilled or filtered water that has no chlorine in it so as not to impart any chlorine flavor to your cubes. Boiling or simmering in hot water leeches off the oak characteristics and flavor that add to structure and will leave your end product lacking.
Lastly, what to do with your chips, cubes, etc when you’re done with them? Take those nicely saturated cubes and put them on the barbeque (you might want to keep them moist to maximize the smoke output) with some good meat (ribs, steak, etc) ice down some drink, and smoke baby smoke!
By P. Bakulic
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