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'''Spontaneous Fermentation''', for the purposes of this article, refers to the inoculation of wort for fermentation with local ambient microbes. This 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 over night. Wild overnight and autochthonous (native) yeast and bacteria are introduced into the wort as it cools. Spontaneous While spontaneous fermentation is part of the traditional brewing method of 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 brewing science for spontaneously fermented beer produced in the Unitied States <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><ref>[https://www.researchgate.net/publication/341353855_The_power_of_sour_-_A_review_Old_traditions_new_opportunities Bossaert, Sofie, et al. “The Power of Sour - A Review: Old Traditions, New Opportunities.” BrewingScience, vol. 72, no. 3-4, 2019, pp. 78–88.]</ref><ref>[https://www.academia.edu/19646963/Brettanomyces_Bruxellensis_Essential_Contributor_in_Spontaneous_Beer_Fermentations_Providing_Novel_Opportunities_for_the_Brewing_Industry Brettanomyces Bruxellensis, Essential Contributor in Spontaneous Beer Fermentations Providing Novel Opportunities for the Brewing Industry. Jan Steensels. BrewingScience, Sept/Oct 2015 (Vol. 68). 2015.]</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" or "open-top fermentation"], which is a general method of fermenting many styles of beer including English ales and lagers in a vessel that is not closed to the atmosphere.
==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 wooden [[Barrel|barrels ]] and/or foedres 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 which are 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 spontaneous native wild-microbe fermentation may also be achieved by ambiently inoculating small amounts of wort and growing up the spontaneously inoculated 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> and , 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. For There is some debate as to whether using spontaneous starters should still be termed "spontaneous fermentation" <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1225800400781505/ MTF Facebook thread about naming]</ref>. Each brewer will have to decide for him or herself what terms to use. We recommend transparency and clarity in descriptions and process to avoid potential confusion. In a stricter sense, beers using active inoculation with spontaneous starters might better be described with terms like 'wild beer', 'beer fermented with native microbes', or a description of the purposes spontaneous starter process rather than entirely "spontaneous beers". Especially if the full wort volume was not ambiently cooled and the starter was allowed to grow for some time before mixing it in. An alternative term for the process itself includes something like "ambient bioprospecting". See [[Spontaneous_Fermentation#Alternative_Applications_of_Spontaneous_Fermentation|alternative applications of this page, beers spontaneous fermentation]] below. Beers receiving additions of isolated cultures or bottle dregs are not treated as spontaneous and are discussed under [[Mixed Fermentation|mixed-culture fermentation]]and [[Commercial_Sour_Beer_Inoculation|commercial sour beer inoculation]]. Ambient bioprospecting (or "spontaneous starters") are discussed in more detail on the [[Wild_Yeast_Isolation#Catching|Wild Yeast Isolation]] page. It has been suggested by some that the terminology of "spontaneous fermentation" is not precise enough for describing the process. Other phrases such as "open-air inoculation", "non-selected fermentation", "ambient inoculation", "coolship ales", and "wild ales" are phrases that some people suggest for alternative nomenclature for spontaneously fermented beer. However, the phrase "spontaneous fermentation" has been widely used by the Belgian lambic brewers to designate this process and the term has been applied in the [https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A52016XC0514%2804%29 EU's TSG law for lambic]. This term has also been widely adopted by the American brewing industry to the point where many brewers and consumers alike recognize the meaning of the phrase "spontaneous fermentation" <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2056705564357647/?comment_id=2057416344286569&comment_tracking=%7B%22tn%22%3A%22R%22%7D Various MTF members. Milk The Funk Facebook group thread on the wording of 'spontaneous fermentation'. 04/12/2018.]</ref>. <gallery>File:Spontaneous starters 2.jpeg|Bioprospecting with an ambient starter File:DSCN2215.JPG|Bioprospecting with an ambient starterFile:Spontaneous starters 3.jpeg|Bioprospecting with an ambient starter</gallery>
==Wort Production==
The traditional production of spontaneously fermented beer employs a few main processes and goals including the production of a dextrinous wort, high hopping rates (usually with aged hops), and inoculation of the wort with by open cooling in a [[coolship]]. Not all breweries producing spontaneously fermented beer employ these three techniques, but they are generally common among producers.
===Mashing===
A dextrinous wort consisting of a high concentration of maltooligosaccharides may be produced by different mashing procedures. The most traditional method of achieving this is through a [[Turbid Mash|turbid mash]]. With this mashing technique, unconverted [[File:Homebrew Turbid Mash Pull.jpeg|200px|thumb|right|First pull of turbid runnings in a homebrew turbid mash]] starchy wort (which is turbid in appearance) is pulled from the mash and heated to denature enzymes. These pulled runnings are then replaced by infusions of hot water as the mash is carried through a series of steps for conversion of the remaining grains. The starchy wort from the early 'turbid' pulls is carried to the boil with incomplete conversion, providing dextrins to sustain ''[[Brettanomyces]] '' and lactic acid bacteria in a prolonged mixed fermentation. Other methods to carry unconverted dextrins into the boil may be employed such as the addition of flour <ref name="Burgundian Babble Belt discussion">[http://www.babblebelt.com/newboard/thread.html?tid=1108752780&th=1243453104 Burgundian Babble Belt discussion]</ref> passing hot mash runnings through flaked grains <ref name="Flat Tail on the Brewing Network">[http://thebrewingnetwork.com/shows/1027/ Flat Tail on the Brewing Network, ~1:04 in]</ref>, or pulling mash runnings before full conversion without the prolonged processing of a turbid mash <ref name="Flat Tail on the Brewing Network" />. Whichever technique is employed, the goals are the same - to provide starches which ''Saccharomyces cerevisiae'' and ''Saccharomyces pastorianus'' cannot ferment and which can feed the diverse combination of other yeasts and bacteria present. Although creating a dextrinous wort is traditional for spontaneous fermentation, it is not necessarily a microbiological requirement. Traditional [[Lambic]] must use a turbid mashing process for the sake of tradition, but non-lambic spontaneous fermentations can also be successful using simpler methods such as single infusion mashes. Not having the dextrins available for the microbes during long-term aging might change the fermentation profile and produce a different type of product (for example, with fewer dextrins there might be less acidity produced from the slow acting ''Pediococcus'', but ''Brettanomyces'' does not rely solely on dextrins to produce its flavor contributions and fewer dextrins will accomplish a faster stable final gravity). Many brewers outside of Belgium have experimented with doing spontaneous fermentation with wort that was not produced from a turbid mash (references needed). Additionally, the maltooligosaccharides produced by turbid mashing can be broken down earlier in the fermentation process by other species such as ''Saccharomyces kudriavzevii'' and acetic acid bacteria <ref name="Bongaerts_2021">[https://pubmed.ncbi.nlm.nih.gov/34232060/ Bongaerts D, De Roos J, De Vuyst L. Technological and Environmental Features Determine the Uniqueness of the Lambic Beer Microbiota and Production Process. Appl Environ Microbiol. 2021 Aug 26;87(18):e0061221. doi: 10.1128/AEM.00612-21. Epub 2021 Aug 26. PMID: 34232060; PMCID: PMC8388830.]</ref>. For more information on turbid mashing, see the [[Turbid Mash|Turbid Mashing]] page.
===Hopping===
Traditional spontaneous Belgian lambic brewers use high hopping rates of aged hops in a long boil (~4 hours or more, which is due to the large volume of sparge water that is used during the [[Turbid Mash|turbid mashing]] process), however, American brewers making spontaneously fermented beer sometimes use a combination of aged and fresh dried hops. Historically, there is [http://www.horscategoriebrewing.com/2016/04/hops-in-spontaneous-fermentation.html some evidence] that lambic brewers used a combination of aged hops and fresh dried hops as well. The high hopping rates help to regulate [[Lactobacillus#Hop_Tolerance|bacterial activity ]] and select for the desired bacteria (''[[Pediococcus]]'' rather than ''[[Lactobacillus]]''). Aging of the hops lowers the flavor/aroma impact the hops provide and also lowers the bitterness. The aged ops hops still do provide some bitterness as both oxidized alpha acids and oxidized beta acids can contribute to perceived bitterness and measured IBUs <ref name="OSU talk at CBC 2015"> Understanding How to Control Flavor and Aroma Consistency in Dry Hopped Beer. Dan Vollmer, Dan Sharp, Dr. Tom Shellhammer (Oregon State University). Oral presentation at the 2015 Craft Brewers Conference</ref>. Cantillon uses hops that are on average 2-3 years old at hopping rate of 250-300g/100 L (30.34334-40.0 40 oz/gal) <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>(~49 minutes in). See also the note about Cantillon's hopping on the [[Cantillon]] wiki page, as actual hopping rates may be slightly higher than the 250-300 g/100 L quoted here. Other producers use such as Oud Beersel report using higher hopping rates <ref> Conversation between Dave Janssen and Gert Christiaens of Oud Beersel, 19-September-2015 </ref>. The use of significantly lower hopping rates may result in less bacterial inhibition and lead to different types of bacteria present. Some lambic producers are experimenting with the use of fresh dried dried hops in addition to or instead of aged hops <ref> [http://www.cantillon.be/br/3_108 Cantillon Iris]</ref> <ref>[https://www.facebook.com/permalink.php?story_fbid=1004839069568069&id=110627652322553 Cantillon Facebook Page post 22-Sept-2015]</ref> <ref>Conversation between Dave Janssen and Jean van Roy of Cantillon, 17-Sept-2015</ref>. James Howat of Black Project Spontaneous Ales uses 0.5 ounces of aged hops per gallon of beer for spontaneously fermented beers brewed using traditional lambic techniques <ref>[https://www.facebook.com/blackprojectbeer/videos/580667305468055/ Howat, James. Facebook live video stream. 12/23/2016. ~5:30 minutes in.]</ref>. For hopping techniques/rates/timing, see [[Hops#Aged_Hops_in_Lambic|Hops in Lambic]].
===Cooling===
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(8-16 hours; extended cooling times of more than a day might lead to mold growth <ref>[https://www.facebook.com/JesterKingBrewery/posts/10154502699393649?comment_id=10154504389923649&reply_comment_id=10154512163043649&comment_tracking=%7B%22tn%22%3A%22R2%22%7D Thread on Jester King Brewery Facebook thread. 01/16/2017.]</ref>). 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>. However the aspect ratios of these sorts of vessels may limit the inoculation of the wort by ambient microbes due to the lower surface area for a given volume compared to traditional coolships. 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 have a low (max nighttime minimum of about -3.9 to 8°C (25-46°F) to appropriately cool the wort overnight <ref>Conversation between Dave Janssen and Armand Debelder of [[3 Fonteinen]], July 2011</ref><ref name="Spontaneous Sour Hour" />(~39 minutes in, ~54 minutes in) 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 wortingWort Souring]], 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 , for example Rob Tod from Allagash Brewing reported solventy and ethyl acetate issues in beers after they were cooled over night at warmer temperatures and aged for 2 years <ref name="Spontaneous Sour Hour"/>(~39 minutes in, ~54 minutes in). Russian River Brewing Company reported that cooling the wort before moving it into the coolship results in softer acidity <ref>[httphttps://www.thebrewingnetworkbeerandbrewing.com/membersarchivepodcast-episode-247-spontaneous-brewing-round-table/sourhour2015_05_wildfriendshipVinnie Cilurzo.mp3 The Sour Hour Episode 11 with Rob Tod Craft Beer and Jason Perkins from Allagash, Jean Van Roy from Cantillon, and Vinnie Cilurzo from Russian RiverBrewing Magazine Podcast episode #147. 07/12/2022. Retrieved 07/17/2022.]</ref>(~39 minutes in, ~54 minutes 27 mins in).
Some more industrial producers of Belgian lambic as well as smaller North American brewers employing spontaneous fermentation acidify their wort to around 4.5 pH before primary fermentation. This may eliminate was done traditionally by acidifying a portion of wort and adding it to the enteric bacteria step mash <ref name="Spitaels et al., 2015">[httphttps://www.sciencedirectstitcher.com/scienceshow/craft-beer-brewing-magazine-podcast/episode/article226-for-cantillons-jean-van-roy-brewing-comes-naturally-90577613 Jean Van Roy. Interview with Craft Beer and Beer Magazine Podcast. Episode #226. 02/pii18/S074000201500012X2022.]</ ref>(~35 mins in). This may eliminate the enteric bacteria step <ref name="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 poisoning, which is a serious concern in the beer, which food industry because of its high level of toxicity; see [https://www.mayoclinic.org/diseases-conditions/botulism/symptoms-causes/syc-20370262 this Mayo Clinic article]). ''Clostridium botulinum'' can grow at the typical pH range of unfermented and unacidified wort and whose 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'', the bacterium responsible for botulism, is gram positive <ref>[https://en.wikipedia.org/wiki/Clostridium_botulinum/ Clostridium botulinum Wikipedia page]</ref>. The degree to which Hop acids might also partially inhibit ''Clostridium botulinum'' might be resistant to the antimicrobial properties and some other gram-positive pathogens <ref>[https://patents.google.com/patent/US6251461B1/en Antimicrobial activity of hops is unknownextract against Clostridium botulinum, Clostridium difficile and Helicobacter pylori. Eric A. Johnson and Gerhard J. Haas. Google Patents (expired). Filed 1997-10-10. Retrieved 05/27/2022.]</ref>. 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><ref>[http://suigenerisbrewing.blogspot.com/2017/01/fact-of-fiction-can-pathogens-survive.html "Fact of Fiction - Can Pathogens Survive in Beer? The RDWHAHB Edition". Bryan of Sui Generis Blog. 01/05/2017. Retrieved 01/16/2017.]</ref>. Whether or not this protects from botulism, it will influence the final beer by preventing enteric bacteria growth. 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 (acidic conditions can trigger exopolysaccharide production in some strains of lactic acid bacteria; see [[Pediococcus#.22Ropy.22_or_.22Sick.22_Beer|''Pediodoccus'']]) <ref name="Spontaneous Sour Hour" /> (~1:10 in). The presence of at least 2-5 ppm of dissolved oxygen (DO) in the wort might also reduce the risk of botulism <ref name="Pérez-Fuentetaja">[https://link.springer.com/article/10.1007/s10750-005-0011-1 Influence of Limnological Conditions on Clostridium Botulinum Type E Presence in Eastern Lake Erie Sediments (Great Lakes, USA). Alicia Pérez-Fuentetaja, Mark D. Clapsadl, Donald Einhouse, Paul R. Bowser, Rodman G. Getchell, W. Theodore Lee. 2006.]</ref>(more references needed); however, the levels of DO in wort that has been cooled in a coolship has not been well studied, and neither has the amount of DO during the first few days of fermentation. Dissolved oxygen in wort that is near boiling temperatures will be limited due to Hentry's law, but some amount of atmospheric oxygen will be absorbed as the wort cools over night <ref>[https://www.boundless.com/physiology/textbooks/boundless-anatomy-and-physiology-textbook/respiratory-system-22/gas-laws-210/henry-s-law-1032-977/ "Henry's Law". Bouldess.com website. Retrieved 03/07/2017.]</ref><ref>[http://docs.engineeringtoolbox.com/documents/639/oxygen-solubility-water-2.png Graph of oxygen solubility in water at different temperatures. Engineering Toolbox website. Retrieved 03/07/2017.]</ref><ref>[https://www.thebrewingnetworkfacebook.com/membersarchivegroups/MilkTheFunk/permalink/1599584193403122/?comment_id=1599693336725541&reply_comment_id=1600361503325391&comment_tracking=%7B%22tn%22%3A%22R%22%7D Bryan of Sui Generis blog. MTF discussion on dissolved oxygen in wort cooled in a coolship, and the accuracy of DO meters. 03/02/sourhour2015_05_wildfriendship2017.mp3 The Sour Hour Episode 11 with Rob Tod ]</ref>. Some reports of DO in wort cooled in a coolship MTF include ~4 ppm in a small coolship that was 2' x 1' x 1', and Jason Perkins from Allagash3.6 - 3.8 ppm in wort cooled overnight in an open 10 gallon boil kettle <ref>[https://www.facebook.com/browse/likes?id=1605741916120683 Amaral, Jean Van Roy Justin. MTF discussion on dissolved oxygen in coolship wort. 03/07/2017.]</ref>. The DO levels from Cantillona commercial sized coolship (10 BBL; 6' x 10') were reportedly 2.6 ppm after the transfer to the coolship while the wort was still hot, and Vinnie Cilurzo from Russian River5.1 ppm after the wort cooled for 14 hours <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1601687793192762/?comment_id=1601698063191735&reply_comment_id=1602191886475686&comment_tracking=%7B%22tn%22%3A%22R1%22%7D Coker, Ryan. MTF discussion on dissolved oxygen in wort cooled in a commercial coolship. 03/07/2017.]</ref> . The dissolved oxygen levels could increase during the filling of the barrels, although there is no data on this that we know of currently. The dissolved oxygen in the wort, however, could be quickly consumed by aerobic bacteria and yeast (which then generally produce a low pH environment that is hostile to ''Clostridium botulinum''). Additionally, some strains of ''C. botulinum'' are more oxygen tolerant than others. Therefore, DO levels should not be relied upon for preventing botulism. Instead, either a timely fermentation is desirable (~1within 4 days has been a suggestion; however, it is not known how long it would take ''C. botulism'' to grow in anaerobic wort and produce enough botulism toxin <ref>[http://beerandwinejournal.com/botulism/ "Storing Wort Runs the Risk of Botulism". Dr. Colby, Chris. Beer and Wine Journal blog. 04/17/2014. Retrieved 03/07/2017.]</ref>, or reducing the pH below 5 before the wort is cooled or immediately after <ref name="Pérez-Fuentetaja" /><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1604630206231854/?comment_id=1605313322830209&reply_comment_id=1605352169492991&comment_tracking=%7B%22tn%22%3A%22R%2312%22%7D Bryan Heit of Sui Generis Blog. MTF discussion on dissolved oxygen in wort cooled in a coolship. 03/07/2017.]</ref>. See also:* [[Coolship]]* [https://www.facebook.com/groups/MilkTheFunk/permalink/1986941961334008/ MTF thread on chilling overnight during warmer than normal temperatures.]* [http:10 //suigenerisbrewing.com/index.php/2020/01/29/botulism-in-beer/ "Fact or Fiction – Botulism in)Beer?" by Dr. Bryan Heit of Sui Generis Brewing] and [http://beerandwinejournal.com/botulism/ "Storing Wort Runs the Risk of Botulism", by Dr. Colby, Chris.]
<gallery>
File:Ky coolship 2.jpg|Homebrew 15 Gallon Coolship
File:Funk Factory Coolship.jpg|30 Barrel Coolship from Funk Factory
File:Drie Fonteinen Coolship.JPG|4 part 2 tier coolship at 3 Fonteinen
File:Cantillon Coolship.jpeg|Cantillon's coolship full of hot wort
File:Homebrew Coolship.jpeg|A homebrew kettle being used as a coolship
</gallery>
====Alternative Approaches to Cooling====
Vinnie Cilurzo from Russian River Brewing Company historically approached cooling differently for his spontaneously fermented "Solambic" beer. Instead of racking boiling wort into a coolship, Cilurzo runs the wort through a heat exchanger and cools the wort to 68°F, and transfers it into a [[Horny Tank|horny tank]] that is housed within the same barrel room as his other (non-spontaneously fermented) beers. Cilurzo claims that this has reduced the acidity of the final beer <ref>[https://beerandbrewing.com/podcast-episode-86-russian-river Vinnie Cilurzo. Craft and Brewing Magazine podcast; Episode 86. 06/07/2019.]</ref> (~20 mins in).
Some lambic brewers have stopped using coolships to cool wort and instead use a plate chiller and then inoculate by moving the cooled wort into a steel tank that has not been CO<sub>2</sub> purged. See [http://www.lambic.info/Brasserie_Mort_Subite#Brewing_Process Brasserie Mort Subite's brewing process] as an example. Logsdon Farmhouse Ales uses a similar technique for their spontaneously fermented ales <ref>Logsdon, Dave. "Sour Power! A Pro Brewer Spontaneous Fermentation Roundtable by Averie Swanson, Dave Logsdon, James Howat, Jeff Mello, and Trevor Rogers". 2018 HomebrewCon presentation.</ref>.
==Fermentation of Spontaneous Beers==
Producers of spontaneously fermented beer typically do not oxygenate their wort <ref name="Beer Temple interview with De Garde"></ref> (~27 minutes in) . Visual signs of fermentation (CO2 production, krausen, bubbles, etc.) generally takes 4-7 days, although we have seen reports of up to two weeks <ref name="howat_comeandbrewit">[http://comeandbrewit.libsyn.com/2016/page/2/size/25 "Episode 34- Sour Beer 102", Come and traditional Brew It podcast. Interview with James Howat from Black Project Spontaneous Ales. 01/07/2016 (~40 minutes in).]</ref><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1183899281638284/ Conversation with Caleb Buck on MTF about spontaneous fermentation. 11/24/2015.]</ref><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1189818124379733/?comment_id=1194393553922190&comment_tracking=%7B%22tn%22%3A%22R3%22%7D Conversation on MTF with Dustin Carver on how long his spontaneous fermentation took to start. 12/14/2015.]</ref><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1213062435388635/?comment_id=1215511598477052&comment_tracking=%7B%22tn%22%3A%22R2%22%7D Conversation on MTF with Mark B. Fry on how long spontaneous fermentation took for him. 01/13/2016.]</ref>. Traditional producers conduct fermentation for a [[File:Homebrew spontaneous fermentation.jpeg|200px|thumb|right|Spontaneous fermentation beginning in a carboy]]long time period (1-3+ years) in wooden vessels. The long fermentation process allows the different microbes present to carry out their slow metabolism of the complex carbohydrates present in the beer, developing the flavors and acidity associated with spontaneous beers (see [[Turbid_Mash#Carbohydrate_Composition_and_Utilization_Through_Fermentation|turbid mashing]] for more) <refname="Van Oevelen et al., 1976">[http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1975.tb06953.x/abstract Van Oevelen et al., 1976. Synthesis of aroma components during the spontaneous fermentation of lambic and gueuze]</ref> <refname="Spaepen et al., 1978">[http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1978.tb03888.x/abstract Spaepen et al., 1978. Fatty acids and esters produced during the spontaneous fermentation of lambic and gueuze]</ref>. The Extended aging in the same vessel as fermentation does not present the same sort of autolysis problems that may be found in 'clean' beers aged for long periods of time on the yeast cake. There are some ideas for why this is the case, such as the extended activity of other microbes taking up autolysis products. It is also possible that the influence of autolysis is found, but that they are expressed differently in these sorts of beers and some say that the autolysis character is an important component of the beers <ref>[http://www.thebrewingnetwork.com/the-sour-hour-episode-9/ Rudy Ghequire from Rodenbach on the Sour Hour]</ref> (~28 minutes in). In Belgian lambic and non-Belgian lambic-style production, the wooden fermentation vessels are frequently used/flavor neutral oak wine barrels in the 220-400 L (58-105 gal) range but other woods such as chestnut are used and the vessels may also be large tuns or foeders foudres holding upwards of 45 HL (about 1200 gal, or about 34 bbl). These barrels provide two primary benefits for the fermentation - they allow a small amount of oxygen permeability and they can provide a an environment which houses some of the microbes active in the fermentation (notably although there is some debate around this, see [[Spontaneous_Fermentation#Notes_on_the_Source_of_Microbes|Sources for Microbes]] below). Notably, ''Brettanomyces, which can penetrate '' could survive some cleaning regimes by penetrating into the wood and in some cases can possibly metabolize compounds present in the wood such as cellobiose, which is produced from toasting of the wood) <refname="Vinnie on the Session Jan 2010">[http://www.thebrewingnetwork.com/post1940/ Vinnie Cilurzo of Russian River on the Brewing Network's Sunday Session, 17-January-2010]</ref>(~3:22 in). While a controlled micro-oxidation can be beneficial to the beer, too much oxygen exposure can lead to excessive acetic acid and/or ethyl acetate production (either from ''Brettanomyces'' or ''Acetobacter'') <ref name="yakobson1">[http://www.brettanomycesproject.com/dissertation/pure-culture-fermentation/pure-culture-fermentation-discussion/ Yakobson, Chad. Pure Culture Fermentation Characteristics of Brettanomyces Yeast Species and Their Use in the Brewing Industry. Pure Culture Fermentation Discussion. 2011.]</ref>. Wooden barrels are usually kept horizontal and full in order to minimize headspace and reduce the growth of aerobic microbes and also reduce the production of acetic acid <ref name="Bongaerts_2021" />. Although wooden barrels used in spontaneous fermetnation production are usually flavor neutral, barrels may still provide flavor and structure from tannins and, in some cases, what they previously held. On a homebrew scale a fair amount of attention has been paid to the topic of oxygen permeability in different fermentation vessels and closures <ref>[https://www.homebrewtalk.com/media/raj-apte-o2-table.58958 Raj Apte's oxygen permeability table]</ref> <ref>[http://www.mocon.com/assets/documents/PPS_Article_highq.pdf Better Bottle closure study]</ref> <ref>[https://www.youtube.com/watch?v=boLqmFIzUZ0&list=PLibE2BjPG_8H0IZe4fS2FD4uidCFhgzBn&index=4 Dan's video discussing airlocks and fermenters]</ref>. It has been suggested that sealing a glass carboy with a wooden dowel or chair leg can result in similar oxygen permeability as a wine barrel. Although this was quite a clever idea for replicating oxygen exposure, this is not recommended as it can lead to breakage of the glass carboys <ref name="Mad Fermentationist Oak">[http://www.themadfermentationist.com/2007/02/8-homebrew-barrel.html Mad Fermentationist $8 homebrew barrel]</ref>. While micro-oxygenation may be an important part of some spontaneous production it may be getting too much attention in homebrew carboy conditions <ref name="Mad Fermentationist Oak">[http://www.themadfermentationist.com/2007/02/8-homebrew-barrel.html Mad Fermentationist $8 homebrew barrel]</ref> (see comments) relative to other controls such as temperature, microbes, and time. See the [[Barrel]] page for discussions on the barrels available to homebrewers. Since spontaneous fermentations can take several days to begin (generally 4-7 days, although we have seen reports of up to two weeks), some professional brewers and a microbiologist have recommended that carboys should be filled as close to the neck as possible to limit the initial headspace and oxygen in that headspace so as to avoid [[mold]] growth (lowering the wort pH to under 4.5 will also help prevent mold growth during the early stages of fermentation) <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1247501295278082/?comment_id=1247509875277224&comment_tracking=%7B%22tn%22%3A%22R%22%7D MTF post regarding mold growth in homebrew spontaneous fermentations. 03/06/2016.]</ref><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1442080252486851/?match=c3BvbnRhbmVvdXMsZmVybWVudGVkLDEwMA%3D%3D MTF post regarding limiting headspace to prevent mold growth. 10/19/2016.]</ref>. Regarding fermentation temperature, commercial producers looking for balanced acidity and flavor/aroma complexity prefer cooler fermentation temperatures in the range of the high 50s to low 60s °F (between 10°C and 20°C) <ref name="Spontaneous Sour Hour" /> (~1:14 in)<ref name="Bongaerts_2021" />. Temperature control is very important to some Lambic producers. 3 Fonteinen had temperature controlled cellars, highlighting the importance of aging temperature. Unfortunately the temperature control thermostat failed and resulted in the brewery nearly going out of business <ref>[https://www.lambic.info/Brouwerij_3_Fonteinen lambic.info 3F]</ref>. This temperature range allows slow and balanced fermentation by the diverse array of microbes present. Warming the fermentation too much results in enhanced production of acidity which is out of line with what the lambic producer is aiming for. This can be used to the advantage of the brewer when producing certain non-lambic inspired spontaneously fermented beers (see below, [[Spontaneous_Fermentation#Alternative_Applications_of_Spontaneous_Fermentation|Alternative applications of spontaneous fermentation]]). American brewers who use coolships for spontaneous fermentation have reported that the success rate for spontaneously fermented beer is around 90-80%. Brewers will often dump undrinkable beers from individual barrels or even beers from barrels that don't meet the expectations of the brewers <ref name="howat_comeandbrewit" />. ===Microbial Succession During Fermentation===[[File:Sofie Bossaert 2019 Fig2.JPG|thumbnail|700px|[https://www.researchgate.net/publication/341353855_The_power_of_sour_-_A_review_Old_traditions_new_opportunities Bossaert, Sofie, et al. “The Power of Sour - A Review: Old Traditions, New Opportunities.” BrewingScience, vol. 72, no. 3-4, 2019, pp. 78–88.]]] ====First Stage: Enterobacteria====The number of different species found in lambic and spontaneously fermented beers is very large and diverse from brewery to brewery and batch to batch, however, scientific research in Belgium and the US has shown a regular general pattern to the microbial succession of spontaneous fermentation beer at the genus level, with only minor genera differences between Belgian lambic beers and American spontaneous ale. This difference is attributed to different microbes being present in different breweries <ref name="Van Oevelen et al., 1977">[http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1977.tb03825.x/abstract/ MICROBIOLOGICAL ASPECTS OF SPONTANEOUS WORT FERMENTATION IN THE PRODUCTION OF LAMBIC AND GUEUZE. Van Oevelen et al., 1977.]</ref><ref name="Bokulic et al., 2012" /><ref name="Spitaels et al., 2014">[http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0095384#pone-0095384-g004/ The Microbial Diversity of Traditional Spontaneously Fermented Lambic Beer. Spitaels et al., 2014. DOI: https://doi.org/10.1371/journal.pone.0095384.]</ref><ref name="Spitaels et al., 2015" /><ref name="Roos_2018_2" /><ref>[http://www2.parc.com/emdl/members/apte/slides_nchf.pdf Raj Apte Concepts of sour Beer, 2004]</ref>. The first stage, which lasts for approximately 1 month <ref name="Van Oevelen et al., 1977" /><ref name="Martens et al., 1992">[http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1992.tb01126.x/abstract/ Martens et al., 1992]</ref>, is dominated by [https://en.wikipedia.org/wiki/Enterobacteriaceae enterobacteria] and [http://laboratoryresearch.blogspot.com/2008/07/yeasts-and-yeastlike-fungi.html?m=1 oxidative yeasts] that produce large amounts of DMS which can be smelled during the early stages of fermentation (see [[Dimethyl Sulfide]] for more details). '''Wort or beer fermenting during this stage should not be consumed due to the fact that some of these are pathogenic bacteria and pose potential health risks.''' Although spontaneous ales have a common pattern of fermentation by groups of genera of microbes, the diversity in specific species is large across different lambic producers and American spontaneous ale producers (although data for American spontaneous ale producers is limited). In American spontaneous ale producers, ''Klebsiella'' spp., ''Enterobacter'' spp.,'' Pectobacterium carotovorum'', and ''Serratia ureilytica'' have been found. In Belgian lambic producers, ''Enterobacter'' spp., such as ''Enterobacter aerogenes'', ''Enterobacter cloacae'', ''Enterobacter hormaechei'' and ''Enterobacter kobei'', ''Klebsiella aerogenes'', ''Klebsiella oxytoca'', ''Klebsiella varicola'', ''Escherichia coli'', ''Hafnia alvei'', ''Hafnia paralvei'', and ''Citrobacter freundii'', have been found in lambic, with ''E. cloacae'' and ''K. aerogenes'' as the most frequently found ones. Although these enterobacteria contribute little in terms of gravity drop over the first month of fermentation (they mostly consume sucrose in the wort), they do contribute aroma and flavor compounds and precursors during the initial stages of spontaneous fermentation, particularly acetoin, 2,3 butanediol, acetic acid, lactic acid, succinic acid, DMS, acetaldehyde, long-chain fatty acids (these play a role in both flavor impact and providing nutrients for yeast later in the fermentation process), and small amounts of glycerol, ethyl acetate, and higher alcohols which might form esters in the later stages of fermentation. Enterobacteria can also contribute to the production of [https://en.wikipedia.org/wiki/Biogenic_amine biogenic amines] in fermented foods and beverages, including spontaneously fermented beers. Enterobacteria usually disappear after 30-40 days of fermentation due to the increase in ethanol, decrease in pH, and a decrease in food availability <ref name="Martens et al., 1992" /><ref name="Roos_2018">[https://www.ncbi.nlm.nih.gov/pubmed/30246252?dopt=Abstract Microbial acidification, alcoholization, and aroma production during spontaneous lambic beer production. Jonas De Roos and Luc De Vuyst. 2018. DOI: 10.1002/jsfa.9291.]</ref>, although one study by Curtin et al. reported finding at least small populations of enterobacteria as late as up to 4.5 months <ref name="curtain_asbc_2018">[https://www.asbcnet.org/lab/webinars/webinars/Pages/funkyFermentationsWebinar.aspx Chris Curtin. ASBC webinar: "Funky Fermentations". 12/12/2018. Retrieved 01/03/2019.]</ref>(~25 minutes in), as well as a significant population of ''Komagataeibacter'', a genera normally found in kombucha, after 135 day <ref name="Curtin_2021">[https://www.tandfonline.com/doi/abs/10.1080/03610470.2020.1795607?journalCode=ujbc20 Avi Shayevitz, Keisha Harrison & Chris D. Curtin (2021) Barrel-Induced Variation in the Microbiome and Mycobiome of Aged Sour Ale and Imperial Porter Beer, Journal of the American Society of Brewing Chemists, 79:1, 33-40, DOI: 10.1080/03610470.2020.1795607.]</ref>. Acetic acid bacteria (AAB) are also present during the first stage of fermentation before alcoholic fermentation begins. These consist of a large diversity of species from ''Acetobacter'' and ''Gluconobacter'', with different species thriving more than others at different points during the long fermentation of lambic and some species found being different in different casks <ref name="De_roos_AAB_2018">[https://journals.asm.org/doi/10.1128/AEM.02846-17 Temporal and Spatial Distribution of the Acetic Acid Bacterium Communities throughout the Wooden Casks Used for the Fermentation and Maturation of Lambic Beer Underlines Their Functional Role. ASM Journals. Applied and Environmental Microbiology. Vol. 84, No. 7. DOI: https://doi.org/10.1128/AEM.02846-17.]</ref>, including two species that were first described by studies researching lambic (''Acetobacter lambici'' and ''Gluconbacter cerevisiae'' sp. nov. <ref>[https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.057315-0 Acetobacter lambici sp. nov., isolated from fermenting lambic beer. Spitaels, Freek and Li, Leilei and Wieme, Anneleen and Balzarini, Tom and Cleenwerck, Ilse and Van Landschoot, Anita and De Vuyst, Luc and Vandamme, Peter. International Journal of Systematic and Evolutionary Microbiology. 2014. https://doi.org/10.1099/ijs.0.057315-0.]</ref><ref>[https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.059311-0 Gluconobacter cerevisiae sp. nov., isolated from the brewery environment Free. Spitaels, Freek and Wieme, Anneleen and Balzarini, Tom and Cleenwerck, Ilse and Van Landschoot, Anita and De Vuyst, Luc and Vandamme, Peter. International Journal of Systematic and Evolutionary Microbiology. 2014. https://doi.org/10.1099/ijs.0.059311-0.]</ref>, as well as ''Acetobacter cerevisiae'' and ''Acetobacter faborum'' <ref name="Roosa_2024">De Roos, J., Vermotea, L., Cnockaertb, M., Vandammeb, P., Weckxa, S., & De Vuysta, L. WOODEN BARRELS HELP TO STEER THE LAMBIC BEER FERMENTATION AND MATURATION PROCESS.</ref>). Acetic acid bacteria are able to grow for the first few weeks because oxygen is available from filling the casks. Once alcoholic fermentation begins, oxygen becomes limited, and the acetic acid bacteria population greatly decreases. Acetic acid bacteria appear again after the alcoholic fermentation phase <ref name="Bongaerts_2021" /><ref name="Roosa_2024"/>. For example, Curtin et al. (2018) reported that acetic acid bacteria came and went at various random points within a 0-4.5 month period of fermentation <ref name="curtain_asbc_2018" />(~26 minutes in). De Ross et al. (2018) reported finding small amounts of acetic acid bacteria in lambic during the first few days of fermentation, which then disappeared once alcoholic fermentation began. AAB then reappeared in the casks in greater numbers at week 7 of fermentation, and continued to be isolated in gradually decreasing cell counts for 24 months, the end of which AAB was no longer isolated <ref name="De_roos_AAB_2018" />. Acidifying the wort to a pH below 4.5 before cooling and exposing to ambient microbes in a coolship can partially eliminate the enterobacteria phase of spontaneous fermentation and thus avoid or limit biogenic amine production, which is a common practice for some lambic breweries <ref name="Spitaels et al., 2015" /><ref name="Roos_2018_2" />. While enterobacteria and oxidative yeasts are not considered to be a part of the core microbes in spontaneous fermentation, it has been shown that ''Saccharomyces cerevisiae'' is metabolically stimulated when co-fermented with some of these species, allowing the ''S. cerevisiae'' to consume more glucose and nitrogen and to more quickly replicate <ref name="Roos_2018" />. De Roos et al (2018) reported significant populations of the enterobacteria species ''Klebseilla variicola'', ''Klebsiella oxytoca'', and the yeast species ''Hanseniaspora uvarum'', ''Saccharomyces cerevisiae'' during the first week or two of lambic fermentation that was pre-acidified (see [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6252343/figure/F3/?report=objectonly Figure 3]). Landschoot et al (2015) sampled lambic wort that was pre-acidified to a pH of 4 after being housed in a coolship overnight and during the early weeks of fermentation and found no ''Enterobacteriaceae'' in the samples <ref name="Landschoot_2015">[https://www.academia.edu/22769494/The_microbial_diversity_of_an_industrially_produced_lambic_beer_shares_members_of_a_traditionally_produced_one_and_reveals_a_core_microbiota_for_lambic_beer_fermentation?email_work_card=view-paper Spitaels, F., Wieme, A. D., Janssens, M., Aerts, M., Landschoot, A. V., Vuyst, L. D., & Vandamme, P. (2015). The microbial diversity of an industrially produced lambic beer shares members of a traditionally produced one and reveals a core microbiota for lambic beer fermentation. Food Microbiology, 49, 23–32. https://doi.org/10.1016/J.FM.2015.01.008.]</ref>. Oxidative yeasts are also present during the first stage of fermentation, including species of ''Rhodotorula'', ''Candida'', ''Cryptococcus'', ''Hanseniaspora'', and ''Pichia'', some of which might survive pre-acidification <ref name="Bokulic et al., 2012" />. Zach Taggart reported that in a spontaneously fermented beer at his commercial brewery this initial stage also corresponded with a pH drop from 5.0 to 4.5 in 6 days and the aroma went from sweet-smelling wort to phenolic and a light burnt rubber character during this time in one batch of spontaneous fermentation <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2360399550654912/ Zach Taggart (using his wife's Facebook account). Milk The Funk Facebook group post on analysis of spontaneous fermentation at 42 North Brewing Co. 11/09/2018.]</ref>.
===Blending (and Dumping)===
[[Blending]] is a fundamental part of traditional spontaneous beer production (and typically of wood aged sour beer production in general). In barrel aged mixed fermentation beer, and especially spontaneously fermented beer, there is a high potential for variability in different barrels/fermentation vessels, even those resulting from the same hot side process. To help create a more balanced and complex product, producers of sour beers often blend barrels (of both the same and of different vintages) together into one final product. In Belgian gueuze production, two and three year old beer is blended with one year old beer. The three/two year old beer contains fermentative microbes while the younger one year old beer contains residual dextrins. Sucrose is often added to the bottles to ensure adequate carbonation (see [[Packaging]]). Packaged Belgian gueuze can age for decades with aromas and flavors continuing to develop during storage <ref name="Bongaerts_2021" />. The homebrewer can employ the same techniques and blend to reach the desired final product from beers of different vintages and different carboys/vessels of the same brew. See the [[blending]] page for more information on this topic.
Frequently, a non-trivial amount of beer is dumped at spontaneous beer breweries <ref>[https://www.youtube.com/watch?v=QUa0QH6niiQ Sour Beer Panel at the Firestone Walker International Beer Fest]</ref> (~8.5 min in). The exact amount depends on the conditions of the brewery and the willingness of the brewer to try to blend in batches that might not taste as good and/or have mild off flavors at the expense of the overall quality of the blend, but commercial brewers have reported dumping levels of 5% (and possibly up to 15%) of total production <ref name="Beer Temple interview with De Garde">[https://vimeo.com/127084279 The Beer Temple Interviews #264 with Trevor Rogers of De Garde]</ref> (~13 minutes in). This may be due to an imbalance in the microbes <ref name="Beer Temple interview with De Garde"></ref> (~14 minutes in) or a bad barrel resulting in off woody flavor <ref name="Spontaneous Sour Hour" /> (~1:31 in) or excessive O2 exposure. In addition to the beer inside such barrels being dumped, the barrel itself is also often discarded <ref name="Beer Temple interview with De Garde"></ref> (~14 minutes in). Homebrewers who are fermenting spontaneously may expect that from time to time they will need to dump a batch.
==Alternative Applications of Spontaneous Fermentation==
Much of the above discussion has focused on spontaneous fermentation as applied to lambic and lambic-inspired brewing. Some brewers are applying spontaneous fermentation to yield beers quite different from lambic-oriented brewers. A notable example of this is [[De Garde]], whose entire lineup of beers are cooled in a coolship and don't see pitched yeast <ref name="Beer Temple interview with De Garde">[https://vimeo.com/127084279 The Beer Temple Interviews #264 with Trevor Rogers of De Garde]</ref> (excepting perhaps a bit of pitched yeast in some beers for bottling conditioning). De Garde produces a range of spontaneous beers including beers similar to Berliner weisse by warm incubation after spontaneous inoculation <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/814831538545062/ MTF facebook conversation with a screenshot of brief De Garde process, March 2014]</ref>. By manipulation of parameters such as grist, hopping levels and incubation/fermentation temperatures, a diverse range of beers of spontaneous fermentation can be produced outside of lambic-inspired beers.
==Alternative Applications of ''=Spontaneous FermentationFrom Fruit===Traditional wine and cider making techniques include not adding any lab microbes, but only relying on the microbes found on the surface of the fruit. This could be considered as a subtype of spontaneous fermentation that is distinct from using a coolship to inoculate wort but is still reliant on the native microflora of the fruit. Rather than a subtype of spontaneous fermentation, this method has also been considered to be more appropriately referred to as "wild inoculation" or "non-selected yeast fermentation" <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2125624937465709/?comment_id=2125655434129326&reply_comment_id=2126302030731333&comment_tracking=%7B%22tn%22%3A%22R%22%7D Justin Amaral. Milk The Funk Facebook group discussion on inoculating wort with fruit. 06/12/2018.]</ref><ref name="ahmed_fruit">[https://www.facebook.com/groups/MilkTheFunk/permalink/2125624937465709/?comment_id=2126549127373290&reply_comment_id=2129101360451400&comment_tracking=%7B%22tn%22%3A%22R%22%7D Tariq Ahmed. Milk The Funk Facebook group discussion on inoculating wort with fruit. 06/14/2108.]</ref>. It is believed by some cider makers that the source for native microbes in their fermentations often comes from the equipment being used to process the cider apples rather than the apples themselves, although there hasn''=t been enough research in this area to know for sure if the major source for native microbes comes from the apples or the equipment used in cider making <ref name="ahmed_fruit" />.
==''Spontaneous Fermentation'' versus ''Mixed Fermentation''==
Spontaneous fermentation yields the greatest diversity of microbes in the wort, including many outside of ''[[Saccharomyces]]'', ''[[Brettanomyces]]'', ''[[Pediococcus]]'' and ''[[Lactobacillus]]'' <ref name="Bokulic et al., 2012">[http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0035507/ Bokulich et al, 2012]</ref> <ref name="Spitaels et al., 2015">[http://www.sciencedirect.com/science/article/pii/S074000201500012X/ Spitaels et al., 2015]</ref> <ref name="Spitaels et al., 2014">[http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0095384#pone-0095384-g004/ Spitaels et al., 2014]</ref>. The degree to which these diverse microbes present during spontaneous fermentation are active and influence the characteristics of the final product is unknown, but brewers report in some cases upwards of 100 distinct microbes present and 24 different microbes which are active and important in producing the character of their beers <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>(~36 minutes in). Spontaneous fermentation may be conducted anywhere, though the microbes present in different environments and/or at different times of the year or from different cooling rates due to different ambient night time temperatures may be better or more poorly suited for producing a good tasting final product <ref name="Beer Temple interview with De Garde">[https://vimeo.com/127084279 The Beer Temple Interviews #264 with Trevor Rogers of De Garde]</ref> <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). In addition, many of the microbes active in commercial spontaneous fermentation derive from the brewery environment <ref name="Bokulic et al., 2012">[http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0035507/ Bokulich et al, 2012]</ref>, which is a benefit that the average homebrewer likely does not have. This great range in the potential of spontaneous fermentation can produce some of the most complex beers in the world, but it can also produce undrinkable products.
Some brewers may opt for the more controlled techniques of [[Mixed Fermentation]] to approach the sorts of characteristics found in spontaneously fermented beers. Mixed fermentation employs the controlled pitching of different lab sourced microbes or bottle dregs. These may be pitched all at once or staggered to control the final product. This greater degree of control can limit some of the risk of poor outcomes and can allow a brewer to better achieve the beer they want; however this approach cannot yield the same microbial diversity of spontaneously fermented beer. For this reason, homebrewers may need to decide what degree of risk they are willing to take and what sort of final product they are after to determine which technique is right for them. Many use a hybridized approach of the two, combining open cooling for spontaneous inoculation with pitching of labs cultures and bottle dregs. While this is technically not spontaneous fermentation and it may yield different results from truly spontaneously fermented beers, it can be a good balance of the benefits of spontaneous fermentation (collection of ambient microbes to express regional terroir and a greater diversity of microbes present) with benefits of mixed fermentation (some pre-screening and greater control in dominant microbes to help select for a final beer of the brewer's preference). Ultimately the brewer must decide which approach, or combination of the two approaches, is right for them with regard to the desired flavor and aroma profile, adherence to tradition, timeframe, and risk of bad beer.
==Media==
===Videos===
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* [https://www.facebook.com/TheBruery/videos/3462243510455831/ The Bruery hosted Facebook live panel on spontaneous fermentation with Jason Perkins from Allagash, Jim Crooks from Firestone Walker, Jeff Stuffings from Jester King Brewery, Bob Kunz from Highland Park Brewery, Brandon Jones from Yazoo Brewing Co., and Keith Pumilia from Brewery Terreux.]
===Podcasts===
* [http://www.thebrewingnetwork.com/the-sour-hour-episode-11/ The Sour Hour podcast detailing spontaneous fermentation process with Rob and Jason from Allagash, Jean Van Roy from Cantillon, and Vinnie from Russian River.]
* [https://beerandbrewing.com/podcast-episode-103-harrison-mccabe-of-beachwood-blendery-creating-the/ Craft Beer and Brewing Podcast: Harrison McCabe of Beachwood Blendery; Creating the Right Environment for Spontaneous and Pitched Culture Wild and Sour Beers.]
==History==
* [http://www.garshol.priv.no/blog/390.html Lars Garshol's write up on the history of people reusing yeast as opposed to spontaneously fermenting.]
==See Also==
===Additional Articles on MTF Wiki===
* [[Turbid Mash]]
* [[Coolship]]
* [[Scientific Publications]]
* [[Gueuze and Lambic Character]]
* [[Dimethyl Sulfide]]
* [[Books]]
* [[Blogs]]
* [[Gueuze]]
* [[Fruit Lambic]]
* [[Cantillon]]
* [[3 Fonteinen]]
* [[De Cam]]
* [[Brettanomyces]]
* [[Pediococcus]]
* [[Oud Bruin]]
* [[Mixed Fermentation]]
* [[Commercial Sour Beer Dregs Inoculation]]
* [[Wild Yeast Isolation]]
===External Resources===
* [http://www.archaicpursuit.com/2018/08/2017-coolship-experiment-hopping-rate.html?m=1 Caleb Buck's collected data on cooling rates, acidity from hopping rates, and other collected data over a multi-year, multi-batch experiment.]* [http://www.stitcher.com/podcast/the-brewing-network/the-sour-hour/e/the-sour-hour-episode-11-37950117 The Sour Hour, Episode 11 with Rob and Jason from Allagash, Jean Van Roy from Cantillon, and Vinnie from Russian River.].* [http://thebrewingnetwork.com/shows/751 Jean Van Roy on The Brewing Network's Sunday Session.]* [http://hwcdn.libsyn.com/p/e/a/2/ea26e00136fe1638/bbr05-30-13cantillon.mp3?c_id=5723890&expiration=1432340356&hwt=a3b044a37355912b46e56da5c64929e5 Jean Van Roy from Cantillon on Basic Brewing Radio.]* [https://www.youtube.com/watch?v=l4i1fyYqIlM&list=PL662949708E13A207 The Lambic Summit: Discussions of lambic with Jean Van Roy of Cantillon, Armand Debelder of 3 Fonteinen, and Frank Boon of Boon.]* [http://www.lambic.info/An_Overview_of_Lambic#Brewing_Lambic Lambic.info page on lambic production.]* [http://www.themadfermentationist.com/2011/04/ambient-spontaneous-yeast-starters.html The Mad Fermentationist on spontaneous yeast starters.]* [http://suigenerisbrewing.blogspot.ca/2013/04/anatomy-of-wild-ferment.html Anatomy of a Wild Ferment; Sui Generis Blog.]* [http://horscategoriebrewing.blogspot.com/2016/02/thoughts-on-spitaels-and-van.html "Thoughts on Spitaels and Van Kerrebroeck et al, 2015", by Dave Janssen on Hors Catégorie Blog - examines microbial and flavor compound evolution over time in bottles of Belgian lambic from Cantillon.]* [https://www.facebook.com/groups/MilkTheFunk/permalink/1300046996690178/ Brandon Jones's notes from CBC 2016 talk on spontaneous fermentation.]* [http://sourbeerblog.com/jester-king-spon-2016-methode-gueuze-tasting-and-interview/ "Jester King 2016 SPON — Méthode Gueuze – Tasting and Interview" on Sour Beer Blog (includes details on process and blending).]* [http://suigenerisbrewing.com/index.php/2018/12/17/coolship-homebrew/ "Going Wild – Coolshipped Beers in the Home Brewery" by Bryan Heit; introduction to spontaneous fermentation with a simpler brewing process (not turbid mashing).]* [https://www.facebook.com/groups/MilkTheFunk/posts/6666386556722835/ List of US breweries that do spontaneous fermentation.]
==References==