13,592
edits
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added study on CO2 influence and CO2 purging
Temperature resistance varies from species to species of ''Clostridium''. Most species have an optimal growth at around 104°F (37°C) <ref>[https://books.google.com/books?id=bA9tAwAAQBAJ&pg=PA232&lpg=PA232&dq=clostridium+butyricum++temperature+range&source=bl&ots=JQLbTobiNS&sig=qfc-2rsj3zOXHf4pGpvP6PW1A90&hl=en&sa=X&ei=-weGVbW-E8WeNtK4gfgP&ved=0CCQQ6AEwATgU#v=onepage&q=clostridium%20butyricum%20%20temperature%20range&f=false Textbook of Microbiology & Immunology. Subhash Chandra Parija. 2nd Edition. Feb 10, 2014.]</ref>. However, ''C. thermosaccharolyticum'' can survive temperatures as hot as 149°F (65°C). Additionally, spores of some species of ''Clostridium'' (such as ''C. tertium'') can survive boiling temperatures for longer than 1.5 hours <ref name="Hawthorne"></ref>.
Carbon dioxide from both fermentation and artificial introduction has been shown to have a stimulatory effect on the growth of ''Clostridium butyricum'' (as well as other bacteria such as ''E. coli'') <ref>[http://eds.b.ebscohost.com/ehost/detail/detail?sid=7c2c7dba-294d-48c3-b771-56332446bf5e%40sessionmgr111&vid=1&hid=103&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#AN=77331781&db=a9h Gaseous CO2 signal initiates growth of butyric-acid-producing Clostridium butyricum in both pure culture and mixed cultures with Lactobacillus brevis. Hakalehto, Elias and Hänninen, Osmo. July 2012.]</ref>. If sanitation issues allow for Clostridium to enter the brewery, CO2 purging may encourage butyric acid formation. Even so, many brewers recommend purging with CO2 during the souring phase of kettle souring to prevent other off-flavors <ref>[http://www.stitcher.com/podcast/the-sour-hour/e/36488361?autoplay=true The Sour Hour on the Brewing Network. Interview with Khris Johnson. Nov 20, 2014.]</ref> (~15 mins in). This might have the benefit of discouraging enteric bacteria from creating off-flavors in the wort.
Although ''C. botulinum'' and other identifiably pathogenic ''Clostridium'' species do not tend to grow in [[Sour Mashing]] conditions, it is advisable to not consume wort produced from a sour mash until after it is boiled. Seek specific food and safety advice from a qualified physician.