Currently, a combination of several factors has created a near
perfect stormfor 2,4,6-TBAformation inwinery cellars: the presence
of a wide variety of 2,4,6-TBP sources, the fact that the
majority of wineries do not have cleaning and sanitation practices
in place to completely prevent colonization of filamentous
microbes on surfaces, and wineries´ need to maintain humid cellars
(to prevent wine evaporation). As with 2,4,6-TCA, once
2,4,6-TBAis released into the atmosphere, it will cling to almost
any surface, and once it gets above a certain threshold in the
atmosphere, it will taint wine.
Sensory Threshold / Sensory Impact of 2,4,6-TBA
The sensory threshold of any chemical compound can vary,
depending on the medium in which it is present (water or alcoholic
solution) and/or on the individual conducting the sensory
evaluation. This is also true for 2,4,6-TBA, which has a sensory
threshold in water ranging from 0.008 to 0.03 ppt, and a threshold
in wine ranging from 2 to 6 ppt. These sensory thresholds in
water and wine are about the same for 2,4,6-TCA.
To give some perspective on the magnitude of such low
concentrations, here are some analogies:
- One ppt is equivalent to one cube of sugar dissolved in
enough water to fill 100 Olympic-size swimming pools.
- One ppt is equal to one second in 31,797 years.
- One ppt is equivalent to 0.4 mm of the total distance from
the Earth to the Moon (238,908 miles).
In wine, depending on the sensitivity of the individual, the
presence of 2,4,6-TBA (or 2,4,6-TCA) will cause a loss of fruit
intensity and aroma at lower concentrations (1 to 3 ppt) and
an actual taint perception at higher concentrations (more
than 3 ppt). At these higher concentrations, 2,4,6-TBA will
impart musty, moldy, wet newspaper, wet cardboard, and
wet cement odors and flavors to wine.
Preventive actions
To prevent haloanisole (2,4,6-TBA, or 2,4,6-TCA) taint in
wineries, the following actions are recommended:
- Perform periodic inspections (semi-annually or annually) to
determine if a facility is free of 2,4,6-TBP, 2,4,6-TBA, 2,4,6-TCP, and
2,4,6-TCA, (plus other haloanisoles and halophenols not discussed
in this column, such as 2,3,4,6-TeCP, 2,3,4,6-TeCA, PCP,
and PCA). The periodic inspections should consist of testing
atmosphere,water supply,water distribution system,wines (both
cellared and those in marketplace), corks, wood material, paint,
and plastic liners.While this is by nomeans a complete list, itwill
provide an effective inspection of a facility.
- Each winery should demand certification from manufacturers
of incoming goods that their products are
haloanisole- and halophenol-free including barrels, oak
adjuncts, silicon bungs, fining agents, and shipping materials
(wood pallets, cardboard, etc).
- When new materials from "unapproved vendors" are
introduced into winery (paint, plastic, or insulation), the
material should be tested for haloanisoles and halophenols.
- Conduct periodic cleaning and sanitation of the winery
infrastructure (floors, walls, ceilings) to limit colonization of
microbes on surfaces.
- Eliminate the use of cleansers and sanitizers containing
chlorine and bromine.
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Conclusion
Due to the plethora of materials that can be origins of the
2,4,6-TBA precursor 2,4,6-TBP, and due to the fact that a very
high percentage (nearly 80%) of all the filamentous fungi
analyzed can produce haloanisoles, the probability of
2,4,6-TBAformation in a winery environment is very high. In
addition, wineries must also contend with the actuality that
2,4,6-TBA can be brought into the facility from external
sources (barrels, paints, wood materials, plastics, etc).
The ubiquitous nature of this chemical requires that wineries
be extremely diligent about prevention activities. As the magnitude
of the 2,4,6-TCA problem in the wine industry demonstrates,
a mere reactive stance toward 2,4,6-TBA could lead
wineries to dramatic economic andmarketing hardships.
References
- Chatonnet, P., S. Bonnet, S. Boutou, and M-D. Labadie. 2004.
“Identification and responsibility of 2,4,6-Tribromoanisole in musty,
corked odors in wine.” J. Agric. Food Chem. 52: 1255-1262.
- Flodin, S., and K. J. Whitfield. 1999. “Biosynthesis of bromophenols
in marine algae.” Water Sci. Technol. 40: 53–58.
- Patnaik, P., E. Powers, and J.N. Khoury. 2002. “Pathways of
phenol-chlorine reactions in the presence of bromide ions in waste
waters.” American Laboratory News, Application Note. August: 26–28.
- Coque, J. J.R., M.L. Alvarez-Rodrigues, and G. Larriba. 2003.
“Characterization of an inducible chlorophenol O-methyltransferase
from Trichoderma longibrachiatum involved in the formation of
chloroanisoles and determination of its role in cork taint of wines.”
Appl. Environ. Microbiol. 69: 5089–5095.
- Alvarez-Rodríguez, M. L., L. López-Ocaña, J.M. López-
Coronado, E. Rodríguez, M. J. Martínez, G. Larriba, and J. J. Coque.
2002. “Cork taint of wines: Role of the filamentous fungi isolated
from cork in the formation of 2,4,6-trichloroanisole by O-methylation
of 2,4,6-trichlorophenol.” Appl Environ. Microbiol. 68: 5860–5869.
- Gribble, G.W. “The diversity of naturally occurring organobromine
compounds.” 1999 Chem. Soc. Rev. 28: 335–346.
- Zoecklein, B. “Environmental taints, Enology Notes #94.”
Wine Enology Grape Chemistry Group, Virginia Tech, Virginia 2004.
- Mara, P.A., and L. F. Bisson. “Bacterial causes of winery
chloroanisole contamination.” Papers and posters presented at the
ASEV 56th Annual Meeting 22–24. June 2005, Seattle, WA.
[Dr. Robert Tracy, with nine years of scientific research experience
and seven years of winery laboratory and quality control/-
quality assurance experience, specializes in wine chemistry and
microbiology, winery sanitation, and QA/QC. He is co-founder of
BevTrac Mobile Quality Systems LLC, based in Windsor, CA
(www.bevtracquality.com), providing a mobile wine laboratory and
consulting services to the wine industry. Please direct inquiries to
robert.tracy@bevtracquality.com or tel: 707/239-8581.]
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