Lager beer fermentation

Oleson, K., Eelding, T., Gjermansen, C., Hansen, J. (2002). The dynamics of the Sacchaomy-cescarlsbergensis brewing yeast transcriptome during production-scale lager beer fermentation. FEMSYeastResearch, 2, 563—573. 

Diacetyl, acetoin, and diketones form during fermentation. Diacetyl has a pronounced effect on flavor, with a threshold of perception of 0.1—0.2 ppm at 0.45 ppm it produces a cheesy flavor. U.S. lager beer has a very mild flavor and generally has lower concentrations of diacetyl than ale. Diacetyl probably forms from the decarboxylation of a-ethyl acetolactate to acetoin and consequent oxidation of acetoin to diacetyl. The yeast enzyme diacetyl reductase can kreversibly reduce diacetyl to acetoin. Aldehyde concentrations are usually 10—20 ppm. Thek effects on flavor must be minor, since the perception threshold is about 25 ppm. 

The results of the AEDA are usually displayed as diagram of the FD-factors vs. the retention indices (RI), the so-called FD-chromatogram. The FD-chromatogram obtained by application of the AEDA on the neutral/basic volatiles of the pale lager beer is shown in Figure 3 [18], The highest FD-factors were found for compounds 4 (malty, alcoholic), 6 (fermented wort), 14 (fruity), 17 (flowery), 20 (spicy) and 22 (cooked apple-like). 

Apparently S. cerevisiae yeast strains are able to carry out only the decarboxylation step (Cogher et al 2004 Tchobanov et al., 2008 Vanbeneden, et al., 2008), which may explain the frequent occurrences of 4-vinylguaiacol and 4-vinylphenol, rather than 4-ethylguaiacol and 4-ethylphenol, in most beer types such as ale and lager. On the other hand, some yeasts of Brettanomyces sp. are capable of carrying out both decarboxylation and reduction steps (Godoy et al., 2009 Tchobanov et al., 2008 Vanbeneden et al., 2008), which may account for the common presence of 4-ethylguaiacol and 4-ethylphenol in specialty beers fermented with Brettanomyces yeasts. 

For production of lagers, the fermentation process is carried out at 7°C to 15°C for 8 to 10 d, and for Pilsners at approximately 20°C for 3 to 5 d. Lagers are almost always fermented with bottom yeast, whereas Pilsners are always fermented with top yeast. Most beers are kept in closed tanks at a temperature of 0°C for 4-6 additional... 

Whatare the different stages during fermentation of lager beers. In which stage does yeast reproduce and in which stage is most of the ethanol produced ... 

Barredo Moguel, L.H., Rojas de Gante, C., and Serna Saldivar, S.O. 2001. Comparisons between a commercial and a waxy sorghum wort fermented into lager beer with emphasis on yeast growth and ethanol production. J. Am. Soc. Brewing Chem. 59(1) 24—27. 

Del Pozo-Insfran, D., Urias-Lugo, D., Hemandez-Brenes, C., and Sema-Saldivar, S.O. 2004. Effect of amyloglucosidase on wort composition and fermentable carbohydrate depletion during fermentation of sorghum lager beer. J. Inst. Brewing. 110(2) 124—132. 

Lager beer A type of beer made using a bottom-fermenting yeast and produced in a relatively slow process that includes lengthy cold storage or lagering. 

Beer taste can be spoiled by contaminating bacteria or yeasts. The most common bacteria are lactic and acetic acid producers and T ymomonas. Wild yeasts can be anything other than the intended strain S. uvarum is considered a contaminant of ale fermentations and S. cerevisiae a contaminant of lager fermentations. The common wild yeast contaminants are S. diastaticus and species of Picbia, Candida and Brettanomjces. It may be noted that the flavor of beer may be improved by the ability of yeast to adsorb bitter substances extracted from hops, such as humulones and isohumulones. 

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