13,594
edits
Changes
update to sanitize
In contrast, Fabrizio et al. (2015) and Cartwright et al. (2018) found that it is possible that steam is an effective way to kill all ''Brettanomyces'' in oak barrels that previously held ''B. bruxellensis'' inoculated wine. Fabrizio et al. (2015) proposed that 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 was demonstrated to be an effective way of killing ''Brettanomyces'' that was found growing as deep as 8 mm 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. Steam treatments that are higher in temperature and longer should not present any concerns to the barrels themselves; however, if hot water is used instead of steam then the longer the water is exposed to the barrel the more character from the barrel that gets removed by the water <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>.
Cartwright et al. (2018) confirmed these results and reported that as little as 12 minutes of steam was enough to eliminate ''Brettanomyces'' in both French and American oak wine barrels that were previously inoculated with ''B. bruxellensis'' for 6 to 7 months. In general, the French oak barrels had larger populations of ''B. bruxellensis'' than the American oak barrels, likely due to American oak being less dense. The staves closest to the bungholes had the largest population of ''B. bruxellensis'' due to better access to oxygen, but there were also large populations within the bottom staves 5-9mm deep. Oak barrels with heavy toast levels tended to have higher populations perhaps due to more cracks in the staves or more availability of cellobiose. The French barrels required 12 minutes and the American oak barrels required only 9 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 with 12 to 20 minutes of 131°F (55°C) to 140°F (60°C) of steam pasteurization <ref name="Cartwright_2018" /><ref>[https://search.informit.com.au/documentSummary;dn=008738882146548;res=IELHSS Zachary Cartwright and Charles Edwards. "Wine maturation: What can a winemaker do about 'Brettanomyces bruxellensis' present in oak barrels?" Wine & Viticulture Journal. Volume 34 Issue 4 (Spring 2019).]</ref>.
Swaffield and Scott (1995) found the yeast and lactic acid bacteria belonging to the genre ''Lactobacillus'', ''Pediococcus'', and ''Leuconostoc'' that were in cider penetrated oak blocks up to 1.25 cm after 9 weeks of being submerged 1 mm into the cider, so it is possible that yeast and bacteria can grow deeper than 8 mm into oak, although these oak cubes were made from virgin oak vats and might not accurately reflect what would be found if these same microbes were inoculated in oak barrels <ref>[https://www.asbcnet.org/publications/journal/vol/Abstracts/bc1995a22.htm Existence and Development of Natural Microbial Populations in Wooden Storage Vats Used for Alcoholic Cider Maturation. C. H. Swaffield and J. A. Scott. 1995. DOI: 10.1094/ASBCJ-53-0117.]</ref>.