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added 5% oxygen disolved in wort can limit botulism formation, with reference
A [[coolship]] is an open vessel used to cool wort by exposure to ambient air which traditional spontaneous fermentation brewers use to both cool their wort and to inoculate the wort with ambient microbes during the open overnight cooling. Traditionally, a coolship is a broad, open-top, flat vessel in which wort cools overnight. The high surface to volume ratio allows for more efficient cooling, which is important at commercial production scales. In addition this broad, shallow design maximizes the area of wort available for inoculation with ambient microbes. On a homebrew scale, where typical batch sizes cool more quickly, a wide shallow pan is not necessary to achieve appropriate cooling overnight given sufficiently low nighttime outdoor temperatures and the use of a wide shallow pan might result in cooling at a much more rapid rate than seen in traditional commercial production. Boil kettles and similarly shaped vessels are sufficient for overnight cooling for most homebrew batch sizes and may provide a rate of cooling more similar to that provided by coolships in commercial production sized batches <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1068826853145528/ Facebook post by James Howat] </ref>. Cantillon targets a cooled wort temp of 18-20 C (64.4-68 F) after the overnight cooling <ref name="Spontaneous Sour Hour" /> (~50 min in). Traditional producers only carry out spontaneous fermentation between fall and spring when nighttime temperatures are sufficiently low (max nighttime minimum of about 8°C <ref>Conversation between Dave Janssen and Armand Debelder of [[3 Fonteinen]], July 2011</ref>) to appropriately cool the wort overnight. The ambient microbial balance may also be more favorable during this time of year (--some sources say there are more acetic acid bacteria in summer--), but inadequate cooling could result in similar results of enhanced acid production (similar to the effect of warm incubation in [[Sour Worting|sour worting]], see also [[Spontaneous_Fermentation#Alternative_Applications_of_Spontaneous_Fermentation|Alternative applications of ''Spontaneous Fermentation'']] below). Whatever the root of the different resulting beers based on time of season/ambient nighttime temperature, producers do report different times of year/temperatures exerting a strong influence on the final beer <ref name="Spontaneous Sour Hour">[http://www.thebrewingnetwork.com/membersarchive/sourhour2015_05_wildfriendship.mp3 The Sour Hour Episode 11 with Rob Tod and Jason Perkins from Allagash, Jean Van Roy from Cantillon, and Vinnie Cilurzo from Russian River]</ref>(~39 minutes in, ~54 minutes in).
Some more industrial producers of Belgian lambic as well as smaller North American brewers employing spontaneous fermentation acidify their wort before primary fermentation. This may eliminate the enteric bacteria step <ref name="Spitaels et al., 2015">[http://www.sciencedirect.com/science/article/pii/S074000201500012X/ Spitaels et al., 2015]</ref> (see below, [[Spontaneous_Fermentation#Microbial_Succession_During_Fermentation|Microbial Succession During Fermentation]]). In addition it may act as a safeguard against ''Clostridium botulinum'' (the bacterium responsible for botulism) in the beer as it can grow at the typical pH range of unfermented and unacidified wort and its spores can survive the boiling process <ref name="James Howat presentation at NHC 2015">[http://www.ahaconference.org/seminars/wild-and-spontaneous-fermentation-at-home James Howat presentation at NHC 2015]</ref>. The degree of botulism risk is not known, though if any reported cases of botulism poisoning from beer exist they are not known to us. Traditional lambic producers have been fermenting unacidified and spontaneously inoculated wort for decades to centuries, which suggests that the risk, if it does exist at all, is very small when following traditional lambic production methods. Furthermore, hops have antimicrobial properties against gram positive bacteria <ref>[http://www.sciencedirect.com/science/article/pii/S0168160503001533/ Sakamoto and Konings, 2003. Beer spoilage bacteria and hop resistance.]</ref> and ''Clostridium botulinum'' is gram positive <ref>[https://en.wikipedia.org/wiki/Clostridium_botulinum/ Clostridium botulinum Wikipedia page]</ref>. The degree to which ''Clostridium botulinum'' might be resistant to the antimicrobial properties of hops is unknown. Some suggest eliminating any potential worry of botulism by acidifying your wort before inoculation <ref name="James Howat presentation at NHC 2015">[http://www.ahaconference.org/seminars/wild-and-spontaneous-fermentation-at-home James Howat presentation at NHC 2015]</ref>. Whether or not this protects from botulism, it will influence the final beer by preventing enteric bacteria growth. The presence of more than 5% oxygen in the wort will also reduce the risk <ref>[http://www.ncbi.nlm.nih.gov/pubmed/15895734 Growth and toxin production by Clostridium botulinum in steamed rice aseptically packed under modified atmosphere. Kasai Y, Kimura B, Kawasaki S, Fukaya T, Sakuma K, Fujii T. May 2005.]</ref>. In addition, acidifying may influence the activity of ''Pediococcus'' in a spontaneously fermented beer, including the development of "sick" beer, and may therefore alter the final beer <ref name="Spontaneous Sour Hour">[http://www.thebrewingnetwork.com/membersarchive/sourhour2015_05_wildfriendship.mp3 The Sour Hour Episode 11 with Rob Tod and Jason Perkins from Allagash, Jean Van Roy from Cantillon, and Vinnie Cilurzo from Russian River]</ref> (~1:10 in).
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