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[[File:LambicInfoDragon.png|right|375px]]
[[An_Overview_of_Lambic|← An Overview of Lambic]]
=Introduction=
The spontaneous fermentation of lambic is a complex process in which non-cultivated yeasts and bacteria present in the environment around the wort take up residence in, and are responsible for the fermentation of, the beer. In contrast to the controlled fermentation found in most other modern beers, spontaneous fermentation involves many different organisms and proceeds through at least four distinct, but often overlapping, stages, each characterized by the dominance of a different set of microbes which are responsible for different aspects of the finished lambic.
=Spontaneous fermentation=
The spontaneous fermentation of lambic is a complex process involving a succession of bacteria and yeasts that progresses along with the chemical changes that occur during fermentation.<ref name=GeuzeKriek>Jef Van den Steen, [[Books#Geuze & Kriek: The Secret of Lambic Beer|Geuze & Kriek: The Secret of Lambic Beer]], 2012</ref> The spontaneous fermentation process has shown considerable variability even among different barrels of beer from the same brewery,<ref name=Spitaels > F. Spitaels, A. D. Wieme, M. Janssens, M. Aerts, H.-M. Daniel, A. Van Landschoot, L. De Vuyst, P. Vandamme [http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0095384 | The Microbial Diversity of Traditional Spontaneously Fermented Lambic Beer], 2000</ref> though all spontaneiously fermented beers appear to follow a general sequence of microbes, which can be broken into four distinct stages:<ref name=AWAs>Nicholas A. Bokulich, Charles W. Bamforth, David A. Mills. [http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0035507|Brewhouse-Resident Microbiota Are Responsible for Multi-Stage Fermentation of American Coolship Ale], PLoS One, 7(4), 2012</ref><ref name=Oevelen77 >D. Van Oevelen, M. Spaepen, P. Timmermans and H. Verachtert, [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], 1977</ref><ref name=Spitaels > F. Spitaels, A. D. Wieme, M. Janssens, M. Aerts, H.-M. Daniel, A. Van Landschoot, L. De Vuyst, P. Vandamme [http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0095384 | The Microbial Diversity of Traditional Spontaneously Fermented Lambic Beer], 2000</ref>
Brettanomyces and other wild organisms, despite often being spoilage organisms in wine, are responsible for some major sensory characteristics of some wine styles.<ref name=Tristezza> M. Tristezza, C. Vetrano, G. Bleve, G. Spano, V. Capozzi, A. Logrieco, G. Mita, F. Grieco [http://www.sciencedirect.com/science/article/pii/S0740002013001408 | Biodiversity and safety aspects of yeast strains characterized from vineyards and spontaneous fermentations in the Apulia Region, Italy], 2013</ref><ref name=Medina> K. Medina, E. Boido, L. Fariña, O. Gioia, M.E. Gomez, M. Barquet, C. Gaggero, E. Dellacassa, F. Carrau [http://www.sciencedirect.com/science/article/pii/S0308814613005025 | Increased flavour diversity of Chardonnay wines by spontaneous fermentation and co-fermentation with Hanseniaspora vineae], 2013</ref> Other minor yeasts found in Lambic, such as Pichia and Kloeckera, have also been found in unspoiled wine.<ref name=Tristezza> M. Tristezza, C. Vetrano, G. Bleve, G. Spano, V. Capozzi, A. Logrieco, G. Mita, F. Grieco [http://www.sciencedirect.com/science/article/pii/S0740002013001408 | Biodiversity and safety aspects of yeast strains characterized from vineyards and spontaneous fermentations in the Apulia Region, Italy], 2013</ref><ref name=Medina> K. Medina, E. Boido, L. Fariña, O. Gioia, M.E. Gomez, M. Barquet, C. Gaggero, E. Dellacassa, F. Carrau [http://www.sciencedirect.com/science/article/pii/S0308814613005025 | Increased flavour diversity of Chardonnay wines by spontaneous fermentation and co-fermentation with Hanseniaspora vineae], 2013</ref>
=Conclusion=
Spontaneous fermentation is a complex process compared to the cultured fermentations of other beers. Several genera of both yeast and bacteria are involved in making the final product. The order in which these organisms dominate the flora allows us to divide the fermentation process into several distinct stages. We have chosen to divide the process into four distinct parts. First, colonization by enteric bacteria, which is responsible for production of acetic acid in the wort, followed by the growth of the yeasts Kloeckera and then Saccharomyces, which ferment most of the simple sugars and produce the majority of the ethanol in Lambic. During the Saccharomyces dominanace of the yeast flora, the bacterial flora switch to primarily lactic acid bacteria, which do exactly what you'd expect something with that name to do. At the end of fermentation, Brettanomyces comes to dominate the yeast flora, and the slow fermentation by these organisms is responsible for many of the odors and flavors associated with Lambic. The aging process then continues well after the beer is bottled. Geographic and seasonal variation, coupled with the "wild" nature of spontaneous fermentation in general, conspires to make Lambic a truely unique product.
=References=
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