chain reaction (PCR), restriction fragment length polymorphism (RFLP), amplified fragment length polymorphism (AFLP), pulsed field gel electophoresis (PFGE), and karyotyping all provide unique genetic fingerprints that distinguish not only between ale and lager yeasts, but also between strains of the same group.
Table 2. Characteristics of Saccharomyces species used in brewing1.
Suc2 Raf Tre Suc Mal Raf Man Eth activity Lys Cad Ety 30°C 37°C
S. bayanus3 S. cerevisiae S. exiguus S. paradoxus4 S. pastorianus5
Adapted from Vaughan-Martini and Martini, 1998
Abbreviations: Suc, sucrose; Raf, raffinose;Tre, trehalose;Mal,maltose;Man,mannose; Eth, ethanol; Lys,lysine; Cad, cadaverine; Ety, ethyl-amine; s, positive, but slow; v, variable; u, undetermined
3synonyms: S. uvarum
4synonyms: S. cerevisiae
5synonyms: S. carlsbergensis v v s v
Box 9—5. Classification of Brewing Yeasts (Continued) References
Dufour, J.-P, K. Verstrepen, and G. Derdelinckx. 2003. Brewing yeast, p. 347—388. In T. Boekhout and V Robert (ed.), Yeasts in food.Woodhead Publishing Limited, Cambridge, England and CRC Press, Boca Raton, Florida.
Hammond,J.R.M., 2003.Yeast genetics,p.67—112. In F.G.Priest and I.Campbell (ed.), Brewing Microbiology, 3rd ed. Kluwer Academic/Plenum Publishers. New York.
Kurtzman, C.P., and J.W. Fell. 1998. Definition, classification and nomenclature of the yeasts. P. 3—5.In C.P. Kutrzman and J.W. Fell (ed.), The Yeast: A Taxonomic Study, 4th Edition. Elsevier Science B.V. The Netherlands.
Vaughan-Martini,A., and A. Martini. 1998. Saccharomyces Meyen ex Reess, 358-371. In C.I? Kurtzman and J.W. Fell (ed.), The Yeast:A taxonomic study, 4th Edition. Elsevier Science B.V.The Netherlands.
Ale (Saccharomyces cerevisiae)
Lager (Saccharomyces pastorianus)
Flocculated yeast rises to the top Optimum growth temperature > 30°C Minimum growth temperature = 15°C Maximum growth temperature = 40°C Cannot metabolize melibiose Slow assimilation of maltotriose Sporulating (at low frequency)
Flocculated yeast settles to the bottom Optimum growth temperature < 30°C Minimum growth temperature = 7°C Maximum growth temperature = 34°C Able to metabolize melibiose Efficient assimilation of maltotriose Non-sporulating
previous fermentation to pitch the next batch. Only when the fermentation appears slow or sluggish or when quality attributes suffer will a new culture be prepared.
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