Changes

While two previous studies have found that steam was not effective at pasteurizing oak barrels, these studies have had their experimental designs criticized by other better designed studies that have found that steam is indeed an effective way to pasteurize oak barrels that previously held ''B. bruxellensis'' inoculated wine. For example, one study inoculated oak chips with nutrient broth instead of using barrels that represented real world conditions, and another study only applied steam for 10 minutes <ref name="Cartwright_2018">[http://www.ajevonline.org/content/early/2018/05/23/ajev.2018.18024 Reduction of Brettanomyces bruxellensis Populations from Oak Barrel Staves Using Steam. Zachary M. Cartwright, Dean A. Glawe, Charles G. Edwards. 2018. DOI: 10.5344/ajev.2018.18024.]</ref>. The most effective and preferred method is to heat the inside of the oak barrel to at least 140°F (60°C) for 20 minutes with hot water or steam. This has been found to be an effective way of killing ''Brettanomyces'' within the wood of 3-year old barrels infected with ''Brettanomyces''. Note that this might not be hot enough to kill other heat tolerant microbes, however, these heat tolerant species tend not to be able to survive in beer. Treatments that are higher in temperature and longer should be fine with steam, however, if hot water is used then the longer the water is exposed to the barrel the more character from the barrel that gets soaked out <ref>[https://www.ncbi.nlm.nih.gov/pubmed/25989358 Heat inactivation of wine spoilage yeast Dekkera bruxellensis by hot water treatment. Fabrizio, Vigentini, Parisi, Picozzi, Compagno, Foschino. 2015.]</ref><ref name="Agnolucci_2017">[https://link.springer.com/article/10.1007/s11274-017-2345-z Brettanomyces bruxellensis yeasts: impact on wine and winemaking. Monica Agnolucci, Antonio Tirelli, Luca Cocolin, Annita Toffanin. 2017.]</ref>. Another study confirmed these results and reported that as little as 12 minutes of steam was enough to pasteurize both French and American oak wine barrels that were inoculated with ''B. bruxellensis'' for 6 to 7 months, with the French barrels requiring 12 minutes and the American oak barrels requiring only 8 minutes at 131°F (55°C). They could not culture ''Brettanomyces'' from the oak even after incubation of stave cross-sections in WRM for 60 days. Although it has been reported that extensive heating can destroy desirable oak flavor compounds such as guaiacol, 4-methylguiaicol, furfural, lactones, eugenol, and vanillin, degradation of these compounds requires temperatures between 248°F (120°C) and 365°F (185°C) for 1 to 6 hours, so significant degradation of desirable oak flavor compounds is not expected to occur at 12 to 20 minutes of 131°F (55°C) to 140°F (60°C) of steam pasteurization <ref name="Cartwright_2018" />.

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