As you craft wines that showcase the nuances of oak, Tastry provides deep visibility on the oak components and the consumer perception of them shaping the flavor profiles of your wines.
Here are the oak-derived compounds included in Tastry wine sample analyses, their detection threshold values used by Tastry, and some information on the role they might play in your wine.
Tastry Perceptual Oak Values and Perception Threshold
Perceptual oak can be used to get a general idea of the human-perceived strength of oak compounds in wine. Perceptual oak is calculated by dividing the concentration of the compound in a solution by its perception threshold value. The value is calculated and reported on the Tastry Insights Dashboard for each oak compound for each of your wines Tastry analyzes. The equation below shows the calculation.
A perception threshold is the average minimum concentration of a substance that is detectable by humans. While some people are more sensitive to certain aroma compounds than others, perception threshold attempts to give an average.
The perception thresholds given for these compounds are an estimation and may vary greatly depending on the particular matrix of a wine. Further, the sensory characteristics of all of these compounds will be expressed differently depending on the flavor matrix of your specific wine. For example, wine chemistry such as titratable acidity, ethanol, and residual sugar all have a considerable impact on the perception thresholds.
Additionally, other flavor compounds will interact with oak in your wine to be perceived differently. Some combinations of oak, for example, will bring out extra fruitiness to your wine, while others will bring out bitterness.
Cis Oak Lactone & Trans Oak Lactone
Cis-oak lactone and trans-oak lactone, sometimes known as whisky lactones, are derived from oak wood lipids. Cis-oak lactone and trans-oak lactone are extracted not only directly from wood but also from precursors called glycoconjugates. Glycoconjugates are extracted into the wine and will react with acids to form cis-oak lactone and trans-oak lactone. This reaction can be relatively slow, meaning cis-oak lactone and trans-oak lactone will increase throughout barrel aging. The compound is more prevalent in American oak, contributing a distinctive coconut aroma. The ratio of native cis-oak to trans-oak lactone will typically be 75%/25%. A light-toasted oak will impart the highest concentrations of cis-oak lactone and trans-oak lactone. Heavy toasting of barrels will decrease the chemical precursors of these compounds.
Eugenol & Isoeugenol
Eugenol and isoeugenol are volatile phenols that originate from the lignin present in oak wood, adding a spicy and clove-like aroma to wines. Like with most volatile phenols, light+ and medium toast barrels will typically impart the highest concentrations of eugenol and isoeugenol. At higher toast levels, eugenol and isoeugenol degrade.
Furfural, Furfuryl Ethyl Ether, and 5-Methylfurfural
Furfural, Furfuryl Ethyl Ether, and 5-Methylfurfural are derived from the polysaccharide’s hemicellulose and cellulose in oak wood. During toasting, hemicellulose, or cellulose, is converted to simple sugars such as xylose or glucose in maillard reactions. The simple sugars then react with hydrogen ions to form furfural and 5-methyl furfural. Furfuryl ethyl ether is formed from the acid-catalyzed dehydration of furfuryl alcohol. With polysaccharides making up 67–70% of dry wood, furfural and its derivatives are abundant in most barrels at all toast levels. Both aging time and toast level will influence how much furfural is extracted from wine. Heavy toasted barrels will impart significantly more furfural than light barrels when aged for extended periods of time (9 months or more). Furfural is most associated with caramel flavors. Furfuryl ethyl ether has been described as odorless or kerosene-scented. 5-Methylfurfural is typically associated with almond flavors.
Guaiacol & 4-Methylguaiacol
Guaiacol and 4-methylguaiacol are volatile phenols formed by the pyrolysis of lignin. Guaiacol is often associated with sweet smoke flavors, while 4-Methylguaiacol is described as an ashy smoke flavor. These compounds are found most abundantly in medium-toasted barrels. In light-toasted barrels, a lower quantity of these compounds is produced. When barrels are more heavily toasted, guaiacol and 4-methylguaiacol will tend to degrade.
Vanillin is also a volatile phenol formed by the pyrolysis of lignin. Vanillin imparts a vanilla aroma and flavor to the wine. Enhanced toasting levels increase the vanillin content; however, heavy toasted oak products may have slightly less vanillin as the compound does degrade with aggressive toasting.
For a full list of characteristics included in each Tastry wine sample analysis, click here.