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Barrels as source of microbes? (<ref name="Spontaneous Sour Hour" /> ~35 min in)
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==Defining ''Spontaneous Fermentation''==
In the most romanticized view of spontaneous fermentation, the microbes which inoculate the wort in the coolship are sourced exclusively from the ambient environment outside the brewery. Scientific publications have suggested that in the case of some producers, these microbes may be resident in the brewhouse <ref name="Bokulic et al., 2012">[http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0035507/ Bokulich et al, 2012]</ref>. This is supported by the reluctance of lambic brewers to alter their facilities (remodeling, moving, painting, etc.) and the spraying of lambic on the walls of new buildings <ref>[https://www.facebook.com/permalink.php?story_fbid=888263374558973&id=110627652322553/ Cantillon Facebook post 5-February-2015]</ref> <ref>[http://www.latisimports.com/assets/uploads/2009/11/MBA_Boon_October_Article.pdf/ Modern Brewery Age Weekly 23-October-2009 Article by Peter Reid with Frank Boon, accessed 7-May-2015]</ref>. The microbes responsible for spontaneous fermentation may also be derived from the oak barrels and/or foedres which are often used to hold the fermenting beer <ref name="Spitaels et al., 2015">[http://www.sciencedirect.com/science/article/pii/S074000201500012X/ Spitaels et al., 2015]</ref>. Many Belgian lambic producers thoroughly clean their barrels using hot water/steam, mechanical agitation (--add Cantillon ref--), and/or burning sulfur <ref> Conversation between Dave Janssen and Steven Sonck of [[De Cam]], winter 2014</ref>; however even the most rigorous cleaning likely does not fully sterilize the barrels. In the case of lambic brewers the microbes resident in barrels are spontaneous in origin, having been derived from years to decades of use in the brewery without any exposure to pitched cultures and the barrels may serve as a concentrating mechanism for the desired cultures. The role of barrels as an inoculating vessel is unclear as some producers report achieving excellent results in barrels new to the brewery and which are microbially clean (<ref name="Spontaneous Sour Hour" /> ~35 min in).
A spontaneous fermentation may also be achieved by inoculating small amounts of wort and growing up the spontaneously inoculated microbes to check for suitability. This is common in homebrew production <ref> [http://www.themadfermentationist.com/2011/04/ambient-spontaneous-yeast-starters.html The Mad Fermentationist Spontaneous Starters, accessed 7-May-2015]</ref> and allows for screening of the microbes to remove wild cultures with aggressive off flavors and/or mold. This is not unlike the potential of used oak barrels, where well performing barrels may be kept to inoculate subsequent batches while poorly performing barrels may be discarded and removed from the brewery. As different microbes survive and thrive in different environments, barrels or pre-screened and grown starters will probably not provide a complete profile of the microbes present in traditional spontaneous fermentation beers. However a combination of a coolship to inoculate the wort with ambient/brewhouse resident microbes combined with a form of pre-screening such as barrel re-use and/or spontaneous starters may provide the full microbiota present in traditional spontaneously fermented products. For the purposes of this page, beers receiving additions isolated cultures or bottle dregs are not treated as spontaneous and are discussed under [[Mixed Fermentation|mixed-culture fermentation]].
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. 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 (---add cutoff temp--) to sufficiently cool the wort overnight. The ambient microbial balance may also be more favorable during this time of year (--some sources say more 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]]). 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 appropriate nighttime outdoor temperatures. Boil kettles and similarly shaped vessels are sufficient for overnight cooling 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>. However the aspect ratio of vessels of this size limit the inoculation of the wort by ambient microbes due to the lower surface area for a given volume compared to traditional coolships.
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