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'''Spontaneous Fermentation''', for the purposes of this article, refers to the inoculation of wort for fermentation with local ambient microbes. There is a long precedence of this term being used by Belgian lambic producers to describe the part of the lambic brewing process where yeast and bacteria inoculate their wort, and the term has been adopted by commercial brewers in other parts of the world to refer to this process <ref>[https://youtu.be/OBrRPbdCln4?t=4m Pierre Tilquin. Youtube interview. 09/16/2013. Retrieved 10/01/2018. ~4 minutes.]</ref><ref>[https://youtu.be/m_OJv5O8YL8?t=2m26s Jean Van Roy. Youtube interview. 03/13/2014. Retrieved 10/01/2018. ~2:26.]</ref><ref>[https://methodetraditionnelle.org/standards/ Méthode Traditionnelle standards. Retrieved 10/01/2018.]</ref>. Spontaneous fermentation is commonly achieved by use of open [[File:Tilquin blowoff tubes.jpeg|400px|thumb|right|Lambic fermenting at Tilquin with blowoff tubes]]cooling such as in a [[coolship]] where the wort is left exposed to the air and allowed to cool naturally overnight and autochthonous (native) yeast and bacteria are introduced into the wort as it cools. While spontaneous fermentation is part of the traditional brewing process for [[Lambic]] <ref>[http://lambicandwildale.com/the-mystery-of-lambic-beer/ The Mystery of Lambic Beer. Jacques De Keersmaecker. Aug 1996. Retrieved 05/05/2015.]</ref><ref name="Roos_2018_2">[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6252343/ Wort Substrate Consumption and Metabolite Production During Lambic Beer Fermentation and Maturation Explain the Successive Growth of Specific Bacterial and Yeast Species. Jonas De Roos, Peter Vandamme, and Luc De Vuyst. 2018. DOI: 10.3389/fmicb.2018.02763.]</ref>, not all spontaneously fermented beers necessarily use other processes that lambic production methods use, and Belgian lambic producers insist that the term "lambic" should only be used for beers brewed in Belgium using the various lambic brewing methods (see [[Lambic#Lambic_outside_of_Belgium.3F|Lambic outside of Belgium]]). Spontaneously fermented beers outside of Belgium have been given names such as "spontaneous ales" <ref>[http://www.blackprojectbeer.com/report/2015/1/28/spontaneous-vs-wild "Spontaneous vs. Wild". Black Project website. 01/28/2015. Retrieved 12/26/2018.]</ref><ref>[https://russianriverbrewing.com/beatification "Beatification". Russian River website. Retrieved 12/26/2018.]</ref>, "spontaneous wild ales" <ref>[http://www.degardebrewing.com/events.html De Garde Brewing website. Retrieved 12/26/2018.]</ref>, "Coolship beers" <ref>[https://www.allagash.com/coolship "Brewing With A Coolship: The Science and Art of Spontaneous Fermentation". Allagash Brewing Company website. Retrieved 12/26/2018.]</ref>, with the term "American Coolship Ales" being the adopted term thus far in scientific literature <ref name="Roos_2018_2" /><ref name="Bokulic et al., 2012">[http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0035507/ Brewhouse-Resident Microbiota Are Responsible for Multi-Stage Fermentation of American Coolship Ale. Bokulich et al, 2012]</ref>. Spontaneous fermentation should not be confused with the various methods of [[Wild_Yeast_Isolation|culturing wild yeast and bacteria]] because many of the microbes that might make a flavor impact during spontaneous fermentation are killed off during the wild yeast culturing processes. Spontaneous fermentation should also not be confused with [https://byo.com/mead/item/1211-open-fermentation-tips-from-the-pros "open fermentation"], which is a generic method of fermenting many styles of beer including English ales and lagers in a vessel that is not closed.
==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 wooden [[Barrel|barrels]] and/or foudres which are often used to hold the fermenting beer, especially if the barrels/foudres have not been thoroughly cleaned <ref name="Spitaels et al., 2015">[http://www.sciencedirect.com/science/article/pii/S074000201500012X/ The Microbial Diversity of Traditional Spontaneously Fermented Lambic Beer. Spitaels et al., 2015]</ref>. Many Belgian lambic producers thoroughly clean their barrels using hot water/steam, mechanical agitation (such as is seen at [[Cantillon]]), 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 which are new to the brewery and microbially clean <ref name="Spontaneous Sour Hour" /> (~35 min in). We do not regard the use of well-cleaned barrels but still containing native microbes from previous use to invalidate spontaneous fermentation
A native wild-microbe fermentation may also be achieved by ambiently inoculating small amounts of wort and growing up caught microbes to check for suitability. This process has often been called a "spontaneous starter" and 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>, however, it is arguably more accurately described as one of the few methods of [http://www.milkthefunk.com/wiki/Wild_Yeast_Isolation bioprospecting]. Bioprospecting from ambient collection allows for the 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 and used to ferment subsequent batches (where the organisms residing in the barrel can exert their influence on the batch) while poorly performing barrels may be discarded and removed from the brewery. This process does differ from oak barrels in that native microbes are cultured and pitched into the wort, rather than the additional inoculation being a result of porous surfaces that have not been fully sanitized. 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.