Microbiology and Biochemistry: Difference between revisions

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IMAGE FROM PAPER

The enteric stage

=The enteric stage=

Lambic wort arrives in the coolship at approximately 5% sugar per weight of water, along with an assortment of proteins and fatty acids and other compounds.<ref name=Erbe >T. Erbe and H. Brückner, [http://www.sciencedirect.com/science/article/pii/S0021967300002557|Chromatographic determination of amino acid enantiomers in beers and raw materials used for their manufacture], 2000</ref> Negligible ethanol is present prior to fermentation, nor is there much of the organic acids that will give lambic its characteristic tartness; the wort has a pH around 5, which is similar to the wort of other beers.<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> Enteric bacteria, including Enterobacter hormaechei, E. kobei, Klebsiella pneumoniae, and Escherichia coli, are the first to gain a foothold in this environment, with significant numbers found after three to four days. The enteric bacteria primarily consume glucose, which reduces the gravity of the wort from ~1.050 to ~1.040 after the first three weeks.

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Brettanomyces inherits the role of most prominant yeast genera from Saccromyces around 8 months, and continues consuming sugar in the wort. Final attenuation can reach over 80% in lambic through the continued action of Brettanomyces, which is often referred to as "overattenuation" or "superattenuation". This is greater than is usually possible with saccromyces alone, as brettanomyces is able to metabolise sugars that saccromyces cannot, generally known as "dextrins".

Brettanomyces has been implicated in producing most of the aroma compounds in Lambic.<ref name="Guinard">Jean-Xavier Guinard, [[Books#Classic Beer Styles: Lambic|Classic Beer Styles: Lambic]], 1990</ref> Sensory-significant quantities of ethyl acetate and ethyl lactate form at this time from ethanol entering into an ester bond with acetic and lactic acid, respectively. The esterization process is greatly helped by the enzyme esterase provided by Brettanomyces.

Brettanomyces has been implicated in producing most of the aroma compounds in Lambic.<ref name="Guinard">Jean-Xavier Guinard, [[Books#Classic Beer Styles: Lambic|Classic Beer Styles: Lambic]], 1990</ref> Sensory-significant quantities of ethyl acetate and ethyl lactate form at this time from ethanol entering into an ester bond with acetic and lactic acid, respectively. The esterization process is greatly helped by the enzyme esterase provided by Brettanomyces. However, the enzymatic esterization is highly reversible and esters found in high concentrations in the lambic prior to the presence of the esterase will achieve a lower equilibrium. This is the case with iso-amyl acetate, which is produced by Saccromyces and is a characteristic odor compound in most other beers.[ref]

Refermentation in the bottle

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 IMAGE FROM PAPER
-The enteric stage
+=The enteric stage=
 Lambic wort arrives in the coolship at approximately 5% sugar per weight of water, along with an assortment of proteins and fatty acids and other compounds.<ref name=Erbe >T. Erbe and H. Brückner, [http://www.sciencedirect.com/science/article/pii/S0021967300002557|Chromatographic determination of amino acid enantiomers in beers and raw materials used for their manufacture], 2000</ref> Negligible ethanol is present prior to fermentation, nor is there much of the organic acids that will give lambic its characteristic tartness; the wort has a pH around 5, which is similar to the wort of other beers.<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> Enteric bacteria, including Enterobacter hormaechei, E. kobei, Klebsiella pneumoniae, and Escherichia coli, are the first to gain a foothold in this environment, with significant numbers found after three to four days. The enteric bacteria primarily consume glucose, which reduces the gravity of the wort from ~1.050 to ~1.040 after the first three weeks.
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 Brettanomyces inherits the role of most prominant yeast genera from Saccromyces around 8 months, and continues consuming sugar in the wort. Final attenuation can reach over 80% in lambic through the continued action of Brettanomyces, which is often referred to as "overattenuation" or "superattenuation". This is greater than is usually possible with saccromyces alone, as brettanomyces is able to metabolise sugars that saccromyces cannot, generally known as "dextrins".
-Brettanomyces has been implicated in producing most of the aroma compounds in Lambic.<ref name="Guinard">Jean-Xavier Guinard, [[Books#Classic Beer Styles: Lambic|Classic Beer Styles: Lambic]], 1990</ref> Sensory-significant quantities of ethyl acetate and ethyl lactate form at this time from ethanol entering into an ester bond with acetic and lactic acid, respectively. The esterization process is greatly helped by the enzyme esterase provided by Brettanomyces.
+Brettanomyces has been implicated in producing most of the aroma compounds in Lambic.<ref name="Guinard">Jean-Xavier Guinard, [[Books#Classic Beer Styles: Lambic|Classic Beer Styles: Lambic]], 1990</ref> Sensory-significant quantities of ethyl acetate and ethyl lactate form at this time from ethanol entering into an ester bond with acetic and lactic acid, respectively. The esterization process is greatly helped by the enzyme esterase provided by Brettanomyces. However, the enzymatic esterization is highly reversible and esters found in high concentrations in the lambic prior to the presence of the esterase will achieve a lower equilibrium. This is the case with iso-amyl acetate, which is produced by Saccromyces and is a characteristic odor compound in most other beers.[ref]
 Refermentation in the bottle