Practical Winery
65 Mitchell Blvd, San Rafael, CA 94903
phone: 415-453-9700 ext 102
email: Office@practicalwinery.com
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November/December 2008
WINE MICROBIOLOGY
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:
  1. One ppt is equivalent to one cube of sugar dissolved in enough water to fill 100 Olympic-size swimming pools.
  2. One ppt is equal to one second in 31,797 years.
  3. 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:
  1. 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.
  2. 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).
  3. When new materials from "unapproved vendors" are introduced into winery (paint, plastic, or insulation), the material should be tested for haloanisoles and halophenols.
  4. Conduct periodic cleaning and sanitation of the winery infrastructure (floors, walls, ceilings) to limit colonization of microbes on surfaces.
  5. Eliminate the use of cleansers and sanitizers containing chlorine and bromine.
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
  1. 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.
  2. Flodin, S., and K. J. Whitfield. 1999. “Biosynthesis of bromophenols in marine algae.” Water Sci. Technol. 40: 53–58.
  3. 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.
  4. 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.
  5. 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.
  6. Gribble, G.W. “The diversity of naturally occurring organobromine compounds.” 1999 Chem. Soc. Rev. 28: 335–346.
  7. Zoecklein, B. “Environmental taints, Enology Notes #94.” Wine Enology Grape Chemistry Group, Virginia Tech, Virginia 2004.
  8. 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.]