Microbiology and Biochemistry: Difference between revisions

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Enteric bacteria are responsible for the production of [[acetic acid]], and the pH of the wort falls from around 5 to 4.5 in the first week of fermentation. The 40 to 120 mg/L acetic acid found in the wort after the first week is very close to the amount found in the final product.<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=sour> J. Edwards and A. DiCaprio. [http://www.process-nmr.com/pdfs/Edwards%20-%20SMASH%202014%20-%20MNova%20Users%20Meeting%20-%209-7-14.pdf| When Beer Goes Sour: An NMR Investigation], Mestrelab

MNova Users Meeting, SMASH – Atlanta, GA, September 7, 2014</ref> Significant changes to the concentration of acetic acid should not occur until the ethanol has a chance to oxidize in aging in the bottle over many years or even decades.<ref name=Vanderhaegen1> B. Vanderhaegen, H. Neven, H. Verachtert, G. Derdelinckx [http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCAQFjAA&url=http%3A%2F%2Fwww.researchgate.net%2Fprofile%2FGuy_Derdelinckx%2Fpublication%2F222839054_The_chemistry_of_beer_aging__a_critical_review%2Flinks%2F0c960523339c4b25a6000000.pdf&ei=Tq3IVKmfFcGyogSs_YLQCA&usg=AFQjCNFaBrvqDGjqEV2I9uQ73dYh_ParXg&sig2=Z8dY4iDHozbT1eb9JeAdrw&bvm=bv.84607526,d.cGU| The chemistry of beer aging – a critical review], 2006</ref> The pellicle that forms on the top of the wort forms around ___ days, and may be the product of acetobacteria during the enteric phase,[9] though most other sources inidcate that the pellicle is the result of Brettanomyces (with Pichia and Candida).<ref name="Guinard">Jean-Xavier Guinard, [[Books#Classic Beer Styles: Lambic|Classic Beer Styles: Lambic]], 1990</ref>

MNova Users Meeting, SMASH – Atlanta, GA, September 7, 2014</ref> Significant changes to the concentration of acetic acid should not occur until the ethanol has a chance to oxidize in aging in the bottle over many years or even decades.<ref name=Vanderhaegen1> B. Vanderhaegen, H. Neven, H. Verachtert, G. Derdelinckx [http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCAQFjAA&url=http%3A%2F%2Fwww.researchgate.net%2Fprofile%2FGuy_Derdelinckx%2Fpublication%2F222839054_The_chemistry_of_beer_aging__a_critical_review%2Flinks%2F0c960523339c4b25a6000000.pdf&ei=Tq3IVKmfFcGyogSs_YLQCA&usg=AFQjCNFaBrvqDGjqEV2I9uQ73dYh_ParXg&sig2=Z8dY4iDHozbT1eb9JeAdrw&bvm=bv.84607526,d.cGU| The chemistry of beer aging – a critical review], 2006</ref><ref name = Werner> Werner, '''2. Het algemene productieproces van bier'''</ref> The pellicle that forms on the top of the wort forms around ___ days, and may be the product of acetobacteria during the enteric phase,[9] though most other sources inidcate that the pellicle is the result of Brettanomyces (with Pichia and Candida).<ref name="Guinard">Jean-Xavier Guinard, [[Books#Classic Beer Styles: Lambic|Classic Beer Styles: Lambic]], 1990</ref>

Low pH (below ~4.5) and an ethanol concentration higher than ~2% by volume is a hostile environment to the enterobacteria, and Saccharomyces species are able to dominate the flora in the wort once these conditions occur around 30-60 days into fermentation.

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 Enteric bacteria are responsible for the production of [[acetic acid]], and the pH of the wort falls from around 5 to 4.5 in the first week of fermentation. The 40 to 120 mg/L acetic acid found in the wort after the first week is very close to the amount found in the final product.<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=sour> J. Edwards and A. DiCaprio. [http://www.process-nmr.com/pdfs/Edwards%20-%20SMASH%202014%20-%20MNova%20Users%20Meeting%20-%209-7-14.pdf| When Beer Goes Sour: An NMR Investigation], Mestrelab
-MNova Users Meeting, SMASH – Atlanta, GA, September 7, 2014</ref> Significant changes to the concentration of acetic acid should not occur until the ethanol has a chance to oxidize in aging in the bottle over many years or even decades.<ref name=Vanderhaegen1> B. Vanderhaegen, H. Neven, H. Verachtert, G. Derdelinckx [http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCAQFjAA&url=http%3A%2F%2Fwww.researchgate.net%2Fprofile%2FGuy_Derdelinckx%2Fpublication%2F222839054_The_chemistry_of_beer_aging__a_critical_review%2Flinks%2F0c960523339c4b25a6000000.pdf&ei=Tq3IVKmfFcGyogSs_YLQCA&usg=AFQjCNFaBrvqDGjqEV2I9uQ73dYh_ParXg&sig2=Z8dY4iDHozbT1eb9JeAdrw&bvm=bv.84607526,d.cGU| The chemistry of beer aging – a critical review], 2006</ref> The pellicle that forms on the top of the wort forms around ___ days, and may be the product of acetobacteria during the enteric phase,[9] though most other sources inidcate that the pellicle is the result of Brettanomyces (with Pichia and Candida).<ref name="Guinard">Jean-Xavier Guinard, [[Books#Classic Beer Styles: Lambic|Classic Beer Styles: Lambic]], 1990</ref>
+MNova Users Meeting, SMASH – Atlanta, GA, September 7, 2014</ref> Significant changes to the concentration of acetic acid should not occur until the ethanol has a chance to oxidize in aging in the bottle over many years or even decades.<ref name=Vanderhaegen1> B. Vanderhaegen, H. Neven, H. Verachtert, G. Derdelinckx [http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCAQFjAA&url=http%3A%2F%2Fwww.researchgate.net%2Fprofile%2FGuy_Derdelinckx%2Fpublication%2F222839054_The_chemistry_of_beer_aging__a_critical_review%2Flinks%2F0c960523339c4b25a6000000.pdf&ei=Tq3IVKmfFcGyogSs_YLQCA&usg=AFQjCNFaBrvqDGjqEV2I9uQ73dYh_ParXg&sig2=Z8dY4iDHozbT1eb9JeAdrw&bvm=bv.84607526,d.cGU| The chemistry of beer aging – a critical review], 2006</ref><ref name = Werner> Werner, '''2. Het algemene productieproces van bier'''</ref> The pellicle that forms on the top of the wort forms around ___ days, and may be the product of acetobacteria during the enteric phase,[9] though most other sources inidcate that the pellicle is the result of Brettanomyces (with Pichia and Candida).<ref name="Guinard">Jean-Xavier Guinard, [[Books#Classic Beer Styles: Lambic|Classic Beer Styles: Lambic]], 1990</ref>
 Low pH (below ~4.5) and an ethanol concentration higher than ~2% by volume is a hostile environment to the enterobacteria, and Saccharomyces species are able to dominate the flora in the wort once these conditions occur around 30-60 days into fermentation.