4-EP/4-EG Technical Bulletin
Related Documents
Brettanomyces Monitoring by Analysis of 4-ethylphenol and 4-ethylguaiacol
New Capabilities:
Brettanomyces yeast are unique in their ability to synthesize the volatile phenols 4-ethylphenol (4-EP) and 4-ethylguaiacol (4-EG). These compounds are an important part of the Brettanomyces character in wine and are important for monitoring Brettanomyces.
ETS Laboratories has offered 4-ethylphenol as a tool for monitoring Brettanomyces in wine since 1993. New methods and equipment now allow reporting of 4-ethylguaiacol as a standard part of the 4-ethylphenol report.
Brettanomyces and Ethyl Phenols
Heresztyn and Chatonnet demonstrated the strong link between 4-EP in wine and Brettanomyces. Subsequent research has shown that Brettanomyces is the only common organism in wine capable of producing 4-ethylphenol. As a unique by-product of infection, 4-EP is an excellent indicator of Brettanomyces presence and activity.
The biosynthesis of ethyl phenols by Brettanomyces is based on the enzymatic conversion of vinyl phenols derived from cinnamic acids.
Early Detection
Analysis of wines for 4-EP enables wineries to identify Brettanomyces populations at very low levels, around 2 col/mL. Knowing that Brettanomyces is present, modest amounts of SO2 can be added to arrest development and the wine can be targeted for monitoring.
Population Control
4-EP can be used to monitor the effectiveness of Brettanomyces control programs in a wine where Brettanomyces is known to exist. First, a baseline concentration of 4-EP is determined. Following treatment, wines with static 4-EP concentrations can be assumed to have inactive populations. Increases indicate continued Brettanomyces activity and ineffective treatment.
Significance of 4-Ethylguaiacol (4-EG)
4-EG is also a valuable indicator of active Brettanomyces populations. As with 4-EP, 4-EG is synthesized from cinnamic acid precursors, but at lower concentrations (the average ratio is 8:1). The aroma profiles of 4-EG and 4-EP are distinctly different. Their combined concentration can be used to estimate the sensory impact of Brettanomyces. Relative concentrations of 4-EG and 4-EP influence the character of Brettanomyces sensory effects. A comparison of ethyl phenol content in selected wines illustrates the importance of their relative concentration.
Graph #1 displays measured concentrations of 4-EP and 4-EG in three wines. In each case, the concentration of 4-EP is fairly consistent. The major difference is the relative concentration of 4-EG. Displayed ratios of 4-EP: 4-EG range from 3:1 to 18:1
Graph #2 presents the same data in terms of the relative sensory impact. “Olfactory Units” are calculated by dividing the concentration by the respective sensory threshold. The results clearly illustrate the significance of 4-EG to the overall sensory impact of Brettanomyces.
Sensory Impact
4-EP and 4-EG are both often described as “phenolic” (like phenol). 4-EP is also described as “medicinal” and “band aid”, while 4-EG is more often described as “spicy” and “smoky”.
4-EG is present in much lower quantities in red wine than 4-EP, typically about 8 times less. However, it is a more volatile compound with a sensory threshold much lower than 4-EP. In a wine with Brettanomyces, both compounds may be well above sensory thresholds.
Perceived Brett character in red wine is influenced by the concentration of both compounds. Variation in the concentration of 4-EG helps to explain why the flavor and intensity of perceived Brett character can be very different with wines having similar 4-EP concentrations.
Analysis for 4-EG in conjunction with 4-EP offers a more complete and superior analytical tool than testing for a single compound. It also offers several advantages over simple colony counts derived from plating wine samples on specialized media.
Plating vs. Ethyl Phenol Analysis
Plating on specialized media followed by microscopic evaluation can be used to monitor Brettanomyces presence and populations. However, there are several limitations to plating which make chemical analysis an attractive adjunct or alternative.
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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Technical Bulletin - Brettanomyces Markers |
Brettanomyces Monitoring by Analysis of 4-ethylphenol and 4-ethylguaiacolNew Capabilities:
Brettanomyces yeast are unique in their ability to synthesize the volatile phenols 4-ethylphenol (4-EP) and 4-ethylguaiacol (4-EG). These compounds are an important part of the Brettanomyces character in wine and are important for monitoring Brettanomyces.
ETS Laboratories has offered 4-ethylphenol as a tool for monitoring Brettanomyces in wine since 1993. New methods and equipment now allow reporting of 4-ethylguaiacol as a standard part of the 4-ethylphenol report.
Brettanomyces and Ethyl Phenols
Heresztyn and Chatonnet demonstrated the strong link between 4-EP in wine and Brettanomyces. Subsequent research has shown that Brettanomyces is the only common organism in wine capable of producing 4-ethylphenol. As a unique by-product of infection, 4-EP is an excellent indicator of Brettanomyces presence and activity.
- 4-EP, in any reportable concentration, indicates the presence of Brettanomyces
- the concentration of 4-EP is related to the concentration of Brettanomyces and its activity
- increases in 4-EP concentration indicate an active Brettanomyces population.
The biosynthesis of ethyl phenols by Brettanomyces is based on the enzymatic conversion of vinyl phenols derived from cinnamic acids.Early Detection
Analysis of wines for 4-EP enables wineries to identify Brettanomyces populations at very low levels, around 2 col/mL. Knowing that Brettanomyces is present, modest amounts of SO2 can be added to arrest development and the wine can be targeted for monitoring.
Population Control
4-EP can be used to monitor the effectiveness of Brettanomyces control programs in a wine where Brettanomyces is known to exist. First, a baseline concentration of 4-EP is determined. Following treatment, wines with static 4-EP concentrations can be assumed to have inactive populations. Increases indicate continued Brettanomyces activity and ineffective treatment.
Significance of 4-Ethylguaiacol (4-EG)
4-EG is also a valuable indicator of active Brettanomyces populations. As with 4-EP, 4-EG is synthesized from cinnamic acid precursors, but at lower concentrations (the average ratio is 8:1). The aroma profiles of 4-EG and 4-EP are distinctly different. Their combined concentration can be used to estimate the sensory impact of Brettanomyces. Relative concentrations of 4-EG and 4-EP influence the character of Brettanomyces sensory effects. A comparison of ethyl phenol content in selected wines illustrates the importance of their relative concentration.
Graph #1 displays measured concentrations of 4-EP and 4-EG in three wines. In each case, the concentration of 4-EP is fairly consistent. The major difference is the relative concentration of 4-EG. Displayed ratios of 4-EP: 4-EG range from 3:1 to 18:1 Graph #2 presents the same data in terms of the relative sensory impact. “Olfactory Units” are calculated by dividing the concentration by the respective sensory threshold. The results clearly illustrate the significance of 4-EG to the overall sensory impact of Brettanomyces.
Sensory Impact
4-EP and 4-EG are both often described as “phenolic” (like phenol). 4-EP is also described as “medicinal” and “band aid”, while 4-EG is more often described as “spicy” and “smoky”.
4-EG is present in much lower quantities in red wine than 4-EP, typically about 8 times less. However, it is a more volatile compound with a sensory threshold much lower than 4-EP. In a wine with Brettanomyces, both compounds may be well above sensory thresholds.
Perceived Brett character in red wine is influenced by the concentration of both compounds. Variation in the concentration of 4-EG helps to explain why the flavor and intensity of perceived Brett character can be very different with wines having similar 4-EP concentrations.
Analysis for 4-EG in conjunction with 4-EP offers a more complete and superior analytical tool than testing for a single compound. It also offers several advantages over simple colony counts derived from plating wine samples on specialized media.
Plating vs. Ethyl Phenol Analysis
Plating on specialized media followed by microscopic evaluation can be used to monitor Brettanomyces presence and populations. However, there are several limitations to plating which make chemical analysis an attractive adjunct or alternative.
- Brettanomyces yeast are not uniformly distributed in tanks or barrels so representative samples are often difficult to obtain.
- Incubation and confirmation can take 14 days.
- Other yeasts with similar growth characteristics can result in false positives.
- Low cell viability due to SO2 additions often results in false negatives.
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.
© 2010 ETS Laboratories. All rights reserved
