Technical Bulletin - ETS Oak Aroma Analysis
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Sophisticated Analytical Capabilities
Aromas from oak aging are an integral part of many fine wines. Oak species and origin, cooperage practices, and winemaking techniques all influence the oak aroma compounds present in a given wine. Analysis of the main aroma components released by oak wood is a key to understanding oak contributions to wine flavor.
ETS Laboratories offers a tool for analysis of the primary oak aroma compounds found in wine. This panel contains nine compounds representing a broad range of chemical classes and sensory effects. The Oak Aroma Analysis has a broad range of applications in winery barrel management, research, and quality control.
Applications
Wine and spirit samples, as well as oak material (chips, shavings or cubes) can be submitted for analysis. Oak material is soaked several days in an “oak free” (unoaked) wine and the resulting soak solution is analyzed.
Suggested Applications
Reporting
The ETS Oak Aroma Analysis is reported in concentrations of µg/L (ppb) for each compound.
Concentrations are also displayed in relationship to a reference by means of a “spider” or “radar” plot. The sample concentrations are expressed as a percentage of reference values that are usually result averages obtained for similar samples.
Sensory descriptors associated with reported compounds are indicated on the plots.
Oak Aroma Compounds
Sensory Impact in Wine
The sensory impact of an aroma compound is commonly evaluated by comparing the concentration found in wine to the sensory threshold determined by adding the pure compound to a model solution or neutral wine. The sensory threshold of a pure compound in model solution does not always adequately describe a compound’s sensory impact in wine since the wine matrix is more complex.
Oak lactones and vanillin frequently exceed published individual thresholds. They are primarily responsible for occurrence of fresh oak, coconut, and vanilla characters in wines.
Other reported compounds are unlikely to reach published sensory thresholds in wine. This does not mean that they do not contribute to wine aroma. Substances with chemical similarities, such as eugenol and isoeugenol, may have additive or cumulative effects.
This also applies to volatile phenols that possess smoky aromas and occur in combination. Guaiacol and 4-methylguaiacol are markers for a complex group of such compounds. Even though their individual concentrations may be well below sensory thresholds, their combined concentrations may result in a perceived sensory effect.
Dramatic synergistic and masking effects between chemically unrelated volatiles have also been demonstrated. The aroma perception of one compound can be enhanced or repressed by the presence of another compound.
This document is a compilation of information and views from various sources provided for the convenience of our clients. Information in this document is provided "as is" without warranty of any kind, either expressed or implied, including but not limited to the warranties of merchantability, fitness for a particular purpose and freedom from infringement. User assumes the entire risk as to the accuracy and the use of this document. This document may be copied and distributed subject to the following conditions: 1) All text must be copied without modification and all pages must be included; 2) All copies must contain ETS's copyright notice and any other notices provided therein; and 3) This document may not be distributed for profit. All trademarks are acknowledged. Copyright ETS Laboratories 2001-2010.
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PTB009-The ETS Oak Aroma Analysis |
Sophisticated Analytical CapabilitiesAromas from oak aging are an integral part of many fine wines. Oak species and origin, cooperage practices, and winemaking techniques all influence the oak aroma compounds present in a given wine. Analysis of the main aroma components released by oak wood is a key to understanding oak contributions to wine flavor.
ETS Laboratories offers a tool for analysis of the primary oak aroma compounds found in wine. This panel contains nine compounds representing a broad range of chemical classes and sensory effects. The Oak Aroma Analysis has a broad range of applications in winery barrel management, research, and quality control.
Applications
Wine and spirit samples, as well as oak material (chips, shavings or cubes) can be submitted for analysis. Oak material is soaked several days in an “oak free” (unoaked) wine and the resulting soak solution is analyzed.
Suggested Applications
- Evaluating barrel trials (wood source, toast level, cooper)
- Monitoring wine aging in barrel (evaluation of same wine over time)
- Fine tuning barrel management (effects of barrel age or sanitation programs)
- Evaluating or managing barrel alternatives (staves, chips, beans)
- Comparisons to benchmark or competitor’s wines
Reporting
The ETS Oak Aroma Analysis is reported in concentrations of µg/L (ppb) for each compound.
Concentrations are also displayed in relationship to a reference by means of a “spider” or “radar” plot. The sample concentrations are expressed as a percentage of reference values that are usually result averages obtained for similar samples.
Sensory descriptors associated with reported compounds are indicated on the plots.
Oak Aroma Compounds
- Lactones (cis and trans) - The main aroma constituents of raw oak are the cis and trans isomers of oak lactone. Their associated sensory descriptors are fresh oak and coconut. The cis isomer is a more powerful aromatic than the trans isomer. American White Oak (Quercus alba) is relatively richer in the cis isomer compared to other oak species. Wood seasoning is reported to affect the relative ratios of cis and trans oak lactones. An increase in barrel toast may reduce the amounts and the sensory impact of oak lactones in wine.
- Vanillin - The main aroma compound in natural vanilla, is also present in raw oak. The quantities of vanillin vary with oak species and seasoning. Vanillin increases with medium toast levels, but may decrease with very high toast. Vanillin is partially transformed to non-aromatic vanillyl alcohol by yeast during barrel fermentation.
- Eugenol and Isoeugenol - Eugenol is the main aroma compound found in cloves. Present in raw oak, eugenol is reported to increase during open-air wood seasoning. Eugenol and isoeugenol possess a very similar spicy, clove-like aroma. Release into wine is reported to increase with toasting level.
- Guaiacol and 4-Methylguaiacol - Wood lignin degradation at very high temperatures (pyrolysis) results in formation of a wide range of volatile phenols including guaiacol and 4-methylguaiacol. These compounds have smoky aromas, and are markers of the smoky character imparted by heavily toasted oak. Guaiacol has a char aroma, while 4-methylguaiacol has both char and spicy characters.
- Furfural and 5-Methylfurfural - Furfural and 5-methylfurfural result from caramelization of cellulose and hemicellulose during barrel toasting. They possess sweet, butterscotch, light caramel, and faint almond-like aromas. They may contribute these characteristics to wines aged in oak and are also markers for the whole family of caramelization compounds.
Sensory Impact in Wine
The sensory impact of an aroma compound is commonly evaluated by comparing the concentration found in wine to the sensory threshold determined by adding the pure compound to a model solution or neutral wine. The sensory threshold of a pure compound in model solution does not always adequately describe a compound’s sensory impact in wine since the wine matrix is more complex.
Oak lactones and vanillin frequently exceed published individual thresholds. They are primarily responsible for occurrence of fresh oak, coconut, and vanilla characters in wines.
Other reported compounds are unlikely to reach published sensory thresholds in wine. This does not mean that they do not contribute to wine aroma. Substances with chemical similarities, such as eugenol and isoeugenol, may have additive or cumulative effects.
This also applies to volatile phenols that possess smoky aromas and occur in combination. Guaiacol and 4-methylguaiacol are markers for a complex group of such compounds. Even though their individual concentrations may be well below sensory thresholds, their combined concentrations may result in a perceived sensory effect.
Dramatic synergistic and masking effects between chemically unrelated volatiles have also been demonstrated. The aroma perception of one compound can be enhanced or repressed by the presence of another compound.
This document is a compilation of information and views from various sources provided for the convenience of our clients. Information in this document is provided "as is" without warranty of any kind, either expressed or implied, including but not limited to the warranties of merchantability, fitness for a particular purpose and freedom from infringement. User assumes the entire risk as to the accuracy and the use of this document. This document may be copied and distributed subject to the following conditions: 1) All text must be copied without modification and all pages must be included; 2) All copies must contain ETS's copyright notice and any other notices provided therein; and 3) This document may not be distributed for profit. All trademarks are acknowledged. Copyright ETS Laboratories 2001-2010.
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