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Research Note

4-Ethylphenol and 4-Ethylguaiacol Concentrations in
Barreled Red Wines from the Okanagan Valley Appellation,
British Columbia
Sierra Rayne1 and Nigel J. Eggers2*
Abstract: 4-Ethylphenol and 4-ethylguaiacol concentrations were determined in 188 barreled red wine samples
from commercial wineries in the Okanagan Valley appellation of British Columbia, Canada using a stable isotope dilution assay (SIDA). 4-Ethylphenol and 4-ethylguaiacol concentrations averaged 56 µg/L and 29 µg/L,
respectively, with >97 to 99% of values below the corresponding odor thresholds for these compounds. Mean
concentrations of the analytes were lower in the Okanagan wines studied than have been previously reported
from other regions. 4-Ethylphenol and 4-ethylguaiacol concentrations were positively correlated with dissolved
oxygen levels and negatively correlated with cellar humidity. No relationships were observed between analyte
concentrations and temperature, length of barrel aging for the wine under study, barrel age, number of rackings,
grape variety, oak type, oak toasting level, and cooper identity.
Key words: wine, 4-ethylphenol, 4-ethylguaiacol, stable isotope dilution assay

Brettanomyces is the asexual, nonspor ulating for m
(Dekkera being the sexual sporulating form) of a yeast
k nown to produce compounds affecting the aroma of
wines, and this microorganism has been the subject of
intensive research over the past several decades (du Toit
and Pretorius 2000, Henick-Kling et al. 2001, Arvik and
Henick-Kling 2002, Coulter et al. 2003, Snowdon et al.
2006, Suarez et al. 2007). Two of the compounds most
closely linked to the Brettanomyces aroma are 4-ethylphenol (4-EP) and 4-ethylguaiacol (4-EG), which are
formed by the microbially mediated decarboxylation of
the corresponding grape-derived hydroxycinnamic acids
( p-coumaric acid and ferulic acid, respectively) (Edlin et
al. 1995, Dias et al. 2003). The aroma of wine spoiled by
Brettanomyces has been described as barnyard, medicinal, Band-aid, and old-leather, and there is considerable
debate as to whether these aromas should be considered a
defect. Because Brettanomyces has the potential to cause
spoilage, it is important to understand the conditions under which 4-ethylphenol and 4-ethylguaiacol develop.

Postdoctoral fellow and 2Associate professor, Chemistry, Earth & Environmental Sciences, Irving K. Barber School of Arts & Sciences, The University
of British Columbia, 3333 University Way, Kelowna, British Columbia, V1V
1V7 Canada.
*Corresponding author (email: nigel.eggers@ubc.ca)
Acknowledgments: This work was supported by the British Columbia Wine
Grape Council, the Investment Agriculture Foundation of British Columbia,
the Western Diversification Program, and local wineries that donated expertise
and samples.
Manuscript submitted December 2006; revised June, August 2007
Copyright © 2008 by the American Society for Enology and Viticulture. All
rights reserved.

The sensory perception thresholds for 4-EP and 4-EG
alone in a red wine are ~ 605 µg/L and 100 µg/L, respectively (Chatonnet et al. 1992). However, when both
compounds were present in a red wine, the sensory perception threshold of 4-EP was lower.
3-Methylbutanoic acid (Licker et al. 1998) and certain tetrahydropyridines (Heresztyn 1986) have also been
shown to play a role in Brettanomyces olfactory defects.
In one study, 4-EP and 4-EG were the main compounds
derived from Brettanomyces that were correlated with
off-odors in red wines, and the concentration of 3-methylbutanoic acid was independent of the concentrations of
these two key spoilage compounds (Coulter et al. 2003).
It appears that 3-methylbutanoic acid may not be directly
responsible for the off-odor attributed to Brettanomyces
but may be involved in additive sensory effects with other Brettanomyces compounds. Sensory assessments and
analyses suggest that the sensory perception threshold of
4-EP depends on the style and structure of the wine, that
is, the concentration and intensity of other wine compounds that could mask (e.g., volatile oak compounds) or
accentuate (e.g., 4-EG) the aroma of 4-EP. For example,
in a light-bodied red wine with little oak inf luence, the
sensory perception threshold of 4-EP may be as low as
~350 µg/L compared with 1000 µg/L in a full-bodied red
wine with intense fruit and considerable oak inf luence
(Coulter et al. 2003).
Brettanomyces spoilage usually arises when wines are
aged or fermented in oak barrels. This yeast only needs
as low as 275 mg/L sugar to fer ment, much less than
the normal levels of residual sugar after the fermentation
has gone dry. Residual sugar in dry red wine can range
between 420 and 1000 mg/L. Brettanomyces grows well

Am. J. Enol. Vitic. 59:1 (2008)

4-EP and 4-EG Concentrations in Barreled Red Wines – 93

under the anaerobic conditions present in barrels during
aging. The rough and uneven surfaces are ideal surfaces
for Brettanomyces to attach and multiply. As oak barrels are porous containers, they are difficult to clean and
sterilize. Although cleaning methods are becoming more
sophisticated (such as water vapor and ozonization), the
microstructure of oak barrels affords a high degree of
protection and provides an environment in which Brettanomyces can survive and be transferred from wine to
wine every time. The high pH of red wine, coupled with
the lower sulfur dioxide levels demanded by the wine
industry, add to these difficulties (Suarez et al. 2007).
Despite the extensive work conducted on these compounds in wine, relatively few studies have documented
their concentrations in commercial vintages from some of
the major winemaking regions, including Australia (Pollnitz et al. 2000a, 200b, Coulter et al. 2003, Henschke
et al. 2004, Hayasaka et al. 2005) and France (Chatonnet et al. 1992). Here we report on concentrations of the
two most well-known Brettanomyces metabolites, 4-ethylphenol and 4-ethylguaiacol, in commercial barreled red
wines from the Okanagan Valley.
The Okanagan Valley appellation, located in southcentral British Columbia, Canada, ~300 kilometers from
the Pacif ic Ocean, is long and nar row and situated at
49 to 50°N latitude. The valley lies in a rain shadow
between two mountain ranges, resulting in low annual
average precipitation that is distributed evenly throughout
the year. Summers are generally hot, with warm average
daily temperatures in July and August (~21.5°C) and with
long daylight hours and high light intensity due to the
northerly latitude, which helps with prolonged daytime
photosynthesis and grape ripening. Winters are generally cold and temperatures can drop below zero for long
periods, with rare events down to -25°C. The valley’s
extensive lakes are important in moderating the otherwise
mountainous/continental climate extremes in summer and
winter. Grape and wine production has increased steadily
in this region over the past two decades and there is significant interest in better understanding potential risks
from sensory defects that can arise from microbial and
yeast infections like Brettanomyces, resulting in the survey data set presented here.

Materials and Methods
Materials. Individual samples (188) of barreled red
wines were collected from 10 commercial wineries in the
Okanagan Valley appellation between June and September
2006. The study design involved the random collection of
samples within each winery from the five major red Vitis
vinifera L. cv. varietals produced in the Okanagan Valley: Cabernet franc (n = 6), Cabernet Sauvignon (n = 38),
Merlot (n = 56), Pinot noir (n = 47), and Syrah (n = 32),
and nine additional samples of a blend of Cabernet franc,
Cabernet Sauvignon, and Merlot. Samples were collected
without the assistance of the winemaker who would have

prior knowledge and potential bias regarding perceived
levels of the analytes.
The number of samples chosen from within each winery was not related to its size or any previous knowledge
of the winery (e.g., history in addressing Brettanomyces growth, perceived quality of the wines produced).
179 wine samples were from the 2005 vintage (length of
time in barrel ranging from 0 to 346 days), six samples
were from the 2004 vintage (collected from two different
wineries; length of time in barrel ranging from 516 to
604 days), and three samples were from the 2003 vintage
(collected from the same winery; length of time in barrel
ranging from 918 to 935 days).
Samples were collected from 225-L oak barrels using
a 50-mL glass volumetric pipette that had been sterilized
with 95% ethanol prior to use, and placed in 50-mL amber glass jars without headspace for transport and storage
before analysis. Samples were stored at 4°C before analysis, with storage times ranging from <24 hr to 30 days.
At the time of sampling, dissolved oxygen (polarographic
probe) and temperature were measured at half-depth in
the barrel using a combined commercial meter (YSI model 55; YSI Incorporated, Yellow Springs, OH) for both
parameters. Temperature was not calibrated at each site,
but meter accuracy was confirmed on a biweekly basis
in the research laboratory using an ice bath (0°C) and
a warm water bath (~30°C) checked against a -50°C to
+150°C mercury thermometer graded in 0.1°C resolution.
The zero-point dissolved oxygen level in the meter was
checked biweekly using deionized water (E-pure grade)
that had been sparged with nitrogen gas under magnetic
stirring for 60 min.
Barrel age, oak type, toasting level, cooper identity,
and length of time in the barrel were obtained directly
from the winemaker/assistant winemaker at each winery
and confirmed with information provided on the barrel.
For 23 samples, neither the barrel age nor length of time
in the barrel being sampled could be obtained. The cooper identity was not available for two samples, the oak
type was unknown for 22 samples, and the toasting level
was unknown for 66 samples. Details regarding the grape
variety and number of rackings prior to sampling were
obtained directly from the winemaker at each winery.
The number of rackings could not be determined for 38
samples. Barrel hygiene methods practiced in the winery
were obtained directly from the winemaker at each winery, but could not be reliably reported for 32 samples.
Cellar humidity was obtained from the in-house climatecontrol station at each winery, but was not available for
79 samples in five wineries that did not control this variable in the cellar.
Analytical methods. A sample of wine (5.00 mL) was
pipetted into a 10-mL test tube containing 2 g sodium
chloride. The sample was spiked with 2.03 µg 4-ethylphenol-d 3 and 2.36 µg 4-ethylguaiacol-d 3 as internal standards. The solution was shaken for 10 sec to ensure mixing, and diethyl ether (2 mL) was added to the vial and

Am. J. Enol. Vitic. 59:1 (2008)

94 – Rayne and Eggers

shaken again for 20 sec. The sample was centrifuged until two distinct layers formed (~2 min). A portion (~1 mL)
of the organic phase was transferred directly from the
test tube to a 3-mL vial, capped, and the extract injected
directly into the gas-chromatograph mass-spectrometer
(GC-MS) under the instr umental conditions described
4-Ethylphenol and 4-ethylguaiacol were analyzed on a
Thermo Scientific Trace GC equipped with an AI 3000
autosampler with 8-position tray (Thermo Fisher Scientific, Waltham, MA) coupled to a Thermo Scientific DSQ
MS. The GC column was an Agilent DB-1701 (14%-cyanopropyl-phenyl)-methylpolysiloxane (Agilent Technologies, Santa Clara, CA) with dimensions of 30 m length
x 0.25 mm i.d. x 0.25-µm film thickness and ultrahighpurity helium at 1.2 mL/min as the carrier gas.
The GC injector was operated in the split/splitless
mode, with a splitless time of 1 min followed by a split
f low of 50 mL/min. The GC injector temperature was
constant at 220°C over the course of a sample run, with
the oven temperature held at 40°C for 1 min, ramped to
260°C at 8°C/min, and held at 260°C for 1 min, for a
total run time of 30 min (with an equilibration time of
0.5 min prior to injection). The MS ion source temperature was 200°C and the GC-MS transfer line temperature
was 250°C. MS scans were obtained in the selected ion
monitoring (SIM) mode operating at unit resolution with
an emission current of 100 µA and a dwell time of 100
ms at each of the following masses: m/z 107, 122, 125,
137, and 155.
Further details regarding synthesis and characterization of the stable isotope derivative internal standards,
sample workup, instrumental conditions, and the criteria
used for identification and quantitation are described in
detail elsewhere (Rayne and Eggers 2007).
Data analysis. For quantitative analysis, concentrations below the method detection limits (MDL; 0.5 µg/L
for 4-ethylphenol and 0.1 µg/L for 4-ethylguaiacol) were
set at one-half the MDL (i.e., 0.25 µg/L for 4-EP and 0.05
µg/L for 4-EG). Relationships between variables were investigated as noted by simple linear regression or the
Tukey-Kramer test with pairwise comparisons for oneway layout design using the statistical software program
KyPlot (v. 2.0 b.15; KyensLab, Tokyo, Japan).

<500 µg/L 4-EP, with 83% of samples having <100 µg/L.
Similarly, 97% of the samples contained <100 µg/L 4-EG,
with 84% of samples having <50 µg/L.
In comparison with concentrations reported from other
regions, the concentrations of 4-EP and 4-EG found in the
Okanagan barreled reds were low, although there is considerable variation in concentrations of these two compounds reported in the literature. In an analysis of 137
red and white wines from France, white wines contained
an average of 3 µg/L 4-EP (range from 0 to 28 µg/L)
compared with red wines with an average of 440 µg/L
(range from 1 to 6047 µg/L) (Chatonnet et al. 1992). The
study also indicated that while some wineries had zero
incidences of phenolic taint, up to half of the vintages of
other wineries had such sensory defects. For the randomly
selected Okanagan barreled red wines we examined, <1%
of the samples would be in the potential range of some
form of 4-EP/4-EG derived phenolic taint.
A survey from Australia examined bottled red wines
of vintages 1986 to 1996 and 1998 barreled red wines.
The reported 4-EP concentrations in the barreled wines
ranged from 385 to 680 µg/L and in the bottled wines
from 2 to 2660 µg/L (mean = 795 µg/L) (Pollnitz et al.
2000a, 2000b). The corresponding ranges of 4-EG were
28 to 45 µg/L in barreled reds and 1 to 437 µg/L (mean =
99 µg/L) in bottled reds. Since that study, researchers at
the Australian Wine Research Institute (AWRI) have continued to monitor levels of these analytes in Australian
wines. A subsequent survey of 303 Cabernet Sauvignon

Results and Discussion
Concentrations of 4-EP and 4-EG were determined in
188 randomly selected samples of barreled red wines from
the Okanagan Valley appellation. Among all samples,
4-EP averaged 56 µg/L (median = 29 µg/L; range from
<0.5 to 544 µg/L) and 4-EG averaged 29 µg/L (median
= 15 µg/L; range from <0.1 to 296 µg/L) (Figure 1). The
majority of samples contained concentrations of these
two analytes well below their respective odor thresholds
(Boidron et al. 1988, Chatonnet et al. 1992, Coulter et
al. 2003). For example, 99.5% of the samples contained

Figure 1 Frequency histograms of 4-ethylphenol and 4-ethylguaiacol
concentrations in Okanagan Valley barreled red wines.

Am. J. Enol. Vitic. 59:1 (2008)

4-EP and 4-EG Concentrations in Barreled Red Wines – 95

and Cabernet Sauvignon-Merlot wines from the vintages
4-EP and 4-EG, demonstrating the need for individual
1996 to 2002 found that mean 4-EP concentrations in the
stable isotope derivatives to reliably quantitate 4-EP and
years between 1996 to 2000 were not different (range
4-EG in wines (Rayne and Eggers 2007).
from 864 to 1164 µg/L), but that concentrations decreased
Among the parameters monitored in addition to analyte
to an average of 490 µg/L for the following 2001 and
concentrations—including dissolved oxygen, temperature,
2002 vintages (Henschke et al. 2004). Recently, the inlength of barrel aging for the wine under study, cellar
cidence of Australian red wines with 4-EP concentrahumidity, barrel age (2000, n = 16; 2001, n = 19; 2002, n
tions above 800 µg/L has been reported to be decreasing
= 11; 2003, n = 46; 2004, n= 19; 2005, n = 46; and 2006,
(Coulter et al. 2003, Hayasaka et al. 2005).
n = 9); and number of rackings (0, n = 95; 1, n = 25; 2, n
Attention has also been paid to the observed ratios
= 21; and 3, n = 9)—dissolved oxygen (positive trending)
of 4-EP to 4-EG concentrations (4-EP:4-EG) in the litand cellar humidity (negative trending) were observed
erature, and the potential diagnostic role of this ratio in
to have statistically significant linear relationships with
possibly separating background levels from Brettanomy4-EP and 4-EG concentrations (Table 1; Figure 2). Disces-derived sources. Early work suggested a possible disolved oxygen has been previously reported to encourage
agnostic ratio of 4-EP to 4-EG concentrations (Chatonnet
Brettanomyces growth (Wijsman et al. 1984, Ciani and
et al. 1992), with the study authors finding a ratio of 8:1
Ferraro 1997, Aguilar Uscanga et al. 2003, Castro-Martiin Brettanomyces-affected wines, which is a similar ratio
nez et al. 2005). The negative relationships between celto the concentrations of the p-coumaric acid (4-hydroxylar humidity and 4-EP/4-EG concentrations suggest that
cinnamic acid) and ferulic acid (4-hydroxy-3-methoxycinthe rate of wine evaporation from the barrel, resulting in
namic acid). A study of Australian red wines found an
more rapid development of a significant headspace and
average 4-EP:4-EG ratio of 8.0 among all varieties, and
oxygen ingress (Singleton 1995, for a review of barrel
the authors reported a decrease in the mean 4-EP:4-EG
aging in this context), could be a relevant determinant
ratio among varieties in the following order: Cabernet
of Brettanomyces risks. In support of this hypothesis,
Sauvignon, 10:1; Syrah/Shiraz, 9:1; Merlot, 8:1; and Pinot
for barrels exposed to ≤65% relative humidity, we find a
noir, 3.5:1 (only the difference in ratios between Syrah/
strong, negative linear correlation (r = -0.44, p < 0.0001)
Shiraz and Pinot noir was noted as statistically signifibetween relative humidity and dissolved oxygen levels. At
cant) (Pollnitz et al. 2000a, 2000b).
≥65% relative humidity, there is no significant correlation
An average 4-EP:4-EG ratio of 3.4 ± 0.5 (± standard
between the two variables (r = 0.21, p = 0.075).
error) was found among all samples having both analytes
No difference in analyte concentrations was found
above the method detection limits (n = 130), with a wide
among the following grape varieties: Cabernet franc (n =
range in ratios from 0.1 to 61. No significant differences
6), Cabernet Sauvignon (n = 38), Merlot (n = 56), Pinot
were found among the following mean 4-EP:4-EG ratios
noir (n = 47), and Syrah (n = 32). These findings are in
by variety: Cabernet Sauvignon, 5.2 ± 2.2; Syrah, 3.8
contrast to others (Pollnitz et al. 2000a), who reported that
± 0.7; Merlot, 3.0 ± 0.5; Pinot noir, 2.4 ± 0.4; and CabAustralian Cabernet Sauvignon wines had higher mean
ernet franc, 1.8 ± 0.7. A positive linear correlation was
concentrations of 4-EP (1250 µg/L) than did Syrah (605
observed between the 4-EP:4-EG ratio and 4-EP concenµg/L) and Pinot noir (338 µg/L). Similarly, we did not
trations (4-EP concentration = 56.2
+ 7.14 × 4-EP:4-EG ratio; r = 0.25,
p < 0.004), with a negative linear
Table 1 Results of statistical tests for relationships between various parameters and
4-ethylphenol (4-EP) and 4-ethylguaiacol (4-EG) concentrations in the Okanagan Valley
cor relation bet ween the 4 -EP:4 appellation barreled red wines.
EG ratio and 4-EG concentrations
4-EP concnc
4-EG concnc
(4-EG concentration = 57.6 – 5.40
Dissolved oxygen
**(m > 0; p < 0.01; r = 0.20)
***(m > 0; p < 10-8; r = 0.41)
× 4-EP:4-EG ratio; r = -0.36, p <
10 ). However, 4 -EP a nd 4 -EG
ns(m = 0; p = 0.64; r = 0.03)
ns(m = 0; p = 0.67; r = 0.03)
levels are still positively correlated
Length of barrel aging
ns(m = 0; p = 0.42; r = 0.06)
ns(m = 0; p = 0.89; r = 0.01)
among all samples having both anCellar humiditya
**(m < 0; p < 0.01; r = -0.25)
*(m < 0; p < 0.05; r = -0.20)
alyte concentrations above detecBarrel agea
ns(m = 0; p = 0.75; r = 0.03)
ns(m = 0; p = 0.76; r = 0.02)
tion limits (4-EG concentration =
Number of rackings
ns(m = 0; p = 0.10; r = -0.14)
ns(m = 0; p = 0.28; r = -0.09)
21.1 + 0.265 × 4-EP concentration;
ns(p > 0.05 all combinations)
r = 0.50, p < 10 , n = 130) indicatb
Barrel cooper
ns(p > 0.05 all combinations)
ns(p > 0.05 all combinations)
ing they are both Brettanomycesderived compounds.
Oak typeb
ns(p > 0.05)
ns(p > 0.05)
The 4-EP:4-EG ratios appear to
Barrel toasting level
ns(p > 0.05)
ns(p > 0.05)
be lower than previously reported
aTested using a standard linear regression model.
in the literature. Recent work has
bTested using the Tukey-Kramer test with pairwise comparisons for one-way layout design.
shown signif icantly different incm: slope of the hypothesized linear regression model; p: probability value that the slope is equal
to zero; r: correlation coefficient; ns: no statistical significance at α = 0.05.
ternal standard recoveries for the
Am. J. Enol. Vitic. 59:1 (2008)

96 – Rayne and Eggers

observe any difference in 4-EP or 4-EG concentrations
between American oak (n = 54) and French oak (n = 112),
nor did we find any significant difference in concentrations based on oak toasting level (medium, n = 56, and
medium plus, n = 33) or among the following 18 coo-

pers: Alain Fouquet (n = 17), Barrel Associates (n = 3),
Berthomieu (n = 13), Dargaud & Jaegle (n = 3), Demptos
(n = 14), Francaise Nadalie (n = 1), Francois Freres (n =
5), J.W. Boswell (n = 5), Keystone Cooperage (n = 2), Mercier (n = 5), Nadalie Tonnellerie (n = 3), Okanagan Barrel
Works (n = 5), Seguin Moreau (n
= 78), Sylvain (n = 10), T.M. T.M.
Mercurey (n = 3), Taransaud (n =
7), Tonnellerie Rousseau (n = 3),
and World Cooperage (n = 11).
General winer y hygiene has
been previously noted as a
means of keeping Brettanomyces
g row t h m i n i m i zed (A r v i k a nd
Hen ick-K li ng 20 02). However,
infected barrels cannot likely be
effectively sterilized because of
their large internal surface areas
and porosity, whether by washing with sulfited water, shaving
and f ir ing, or ozone t reat ment
(Pollnitz et al. 2000a, Arvik and
Henick-Kling 2002), with Brettanomyce s fou nd as deep as 8
mm into the oak wood (MalfeitoFerreira et al. 2004). Among the
seven barrel hygiene procedures
re por ted to us by w i nema ker s
during our study (including the
use of new bar rels with no hyg ie ne t reat me nt), st ea m t reatment with SO 2 gas appeared to
result in the lowest mean 4-EP
and 4-EG concentrations (Table
2). The use of steam as par t of
a ba r rel hyg iene prog ra m t hat
re su lt s i n opt i mu m sa n it at ion
versus competing nonsteam approaches has been repor ted beFigure 2 Relationships between dissolved oxygen, wine temperature, and length of barrel aging and
fore ( Malfeito -Fer rei r a 20 05).
4-ethylphenol and 4-ethylguaiacol concentrations in Okanagan Valley barreled red wines.
Conversely, treatment using 5%
potassium metabisulfite solution
w it h oz on at ion a nd hot wat e r
Table 2 Summary of Tukey-Kramer tests with pairwise comparisons for one-way layout
design on 4-ethylphenol (4-EP) and 4-ethylguaiacol (4-EG) concentrations between differing
t reat ment generally cor relates
barrel hygiene procedures. Values are mean concentrations with standard error about the
with wines having higher avermean for each analyte-barrel hygiene procedure combination.
age concentrations of 4-EP and
4-EP concn
4-EG concn
4-EG (Table 2). However, there
are many factors that can inf lu100°C water for 2 min + 5% potassium metabisulfite
32.2 ± 12.2 acd
23.5 ± 7.2 ab
ence Brettanomyces g row th i n
solution and 2% citric acid solution storage (n = 16)
wines during barrel aging (e.g.,
72°C water + ozonation (n = 31)
73.1 ± 18.7 abc
45.1 ± 9.5 b
dissolved oxygen, SO2 levels, pH,
Cold water + 5% potassium metabisulfite solution (n = 14)
71.0 ± 20.0 abcd
33.5 ± 9.8 ab
temperature, ethanol content, reNew barrel with no previous use or cleaning (n = 12)
55.3 ± 10.8 abcd
48.5 ± 23.6 b
sidual sugar, and nutrients such
5% Potassium metabisulfite solution with ozonation and
147.2 ± 18.1 b
49.0 ± 8.6 ab
as nitrogen) (Henick-Kling et al.
hot water treatment (n = 6)
2001, A r vi k and Henick-K ling
Steam treatment with SO2 gas (n = 38)
17.2 ± 5.0 d
3.6 ± 1.0 a
2002, Silva et al. 2004), so we
aValues followed by the same letter are not significantly different at α = 0.05.
cannot make a def initive stateAm. J. Enol. Vitic. 59:1 (2008)

4-EP and 4-EG Concentrations in Barreled Red Wines – 97

ment as to an optimum bar rel hygiene treatment that
encompasses all these factors. However, steam treatment
with SO 2 gas appears to result in the lowest mean 4-EP
and 4-EG concentrations of the various barrel hygiene
procedures used for the wines in this study.


Edlin, D.A.N., A. Narbad, J.R. Dickinson, and D. Lloyd. 1995.
The biotransformation of simple phenolic compounds by Brettanomyces anomalus. FEMS Microbiol. Lett. 125:311-316.
Hayasaka, Y., G.A. Baldock, and A.P. Pollnitz. 2005. Contributions
of mass spectrometry in the Australian Wine Research Institute
to advances in knowledge of grape and wine constituents. Aust.
J. Grape Wine Res. 11:188-204.

Concentrations of 4-ethylphenol and 4-ethylguaiacol in
barreled red wines (n = 188) from commercial wineries
in the Okanagan Valley appellation averaged 56 µg/L and
29 µg/L, respectively, with >97 to 99% of values below
the corresponding odor thresholds for these compounds.
4-Ethylphenol and 4-ethylguaiacol concentrations were
positively correlated with dissolved oxygen levels and
negatively correlated with cellar humidity. No relationships were observed between analyte concentrations and
temperature, length of barrel aging for the wine under
study, barrel age, number of rackings, grape variety, oak
type, oak toasting level, or cooper identity. Among the
various barrel hygiene procedures used for the wines in
the study, steam treatment with sulfur dioxide gas appeared to result in the lowest mean 4-ethylphenol and
4-ethylguaiacol concentrations.

Henick-Kling, T., C. Egli, J. Licker, and T.E. Acree. 2001. Brettanomyces in wine. In Proceedings of the 30th Annual New York
Wine Industry Workshop. T. Henick-Kling (Ed.), pp. 67-79. N.Y.
State Agricultural Experiment Station, Geneva.

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