Just to back track a little about professional literature and suggested pitching temp here is an excerpt from the MBAA Practical handbook For The Specialty Brewer Vol. 2
"(ale) pitching temperature is typically 59°-62°F (15°-17°C), climbing to 67°-70°F (20°-22°C)..."
That is still not lager temperature. It is just merely cool ale temperature. The question to ask here is why? What is gained? I know what is lost. The optimal replication temperature for Saccharomyces cerevisiae is 30C. At 30C, the average replication period is 90 minutes. Every degree below 30C extends the replication period.
... and for lager
"Wort is cooled to 45°F (7°C), aerated to a DO content of 8 ppm, and pitched... as the beer ferments, the temperature rises"
First off, fermentation temperature only rises if it is allowed to rise, which applies to both lager and ale fermentation. Are these practices from the days when fermentation temperature could not be precisely controlled; thereby, helping to prevent thermal overshoot? Secondly, there are two different families of lager yeast with different optimum fermentation temperatures; therefore, this practice is based more on brewing dogma than science, especially in light of recent findings with respect to yeast genetics. If one reads the publication I linked in my last post, one will see that only the Saaz family of lager strains exhibits significant cryotolerance. In the case of Saaz strains optimum temperature is 10C/50F whereas optimum temperature for Frohberg strains is 22C/72F, which is at the higher end of normal ale temperatures. Can we lower the temperature to retard fermentation to reduce growth-related metabolites? Absolutely! However growth-related metabolites are dependent on things other than temperature. Attributes such as protein content and dissolved O2
enter the picture because higher alcohol production is the result of catabolism of amino acids (the building blocks of protein) via the Erhlich pathway and O2
has an effect of acetic acid production. That means that treating higher alcohol and ester production as only a fermentation temperature-related problem is akin to treating the symptoms instead of fixing the problem. The carbon to nitrogen ratio of the wort as well as the amount of dissolved O2
have a major impact on higher alcohol and acetic acid production. In essence, high FAN coupled with low O2
is recipe for hot tasting, estery beers. Fermenting at lower temperature to control higher alcohol and ester production is akin to putting a band-aid on a sucking chest wound. If anyone wants to test this phenomenon, formulate two non-excessively hopped beers at a gravity of 1.060 (i.e., the malt and hops need to be in balance). The first beer should be all malt. The second beer should contain 20 to 30% flaked maize. The all-malt beer is splash aerated. The adjunct beer is venturi or direct O2
injection aerated. One will have to adjust the hopping rate down on the adjunct beer to accommodate for its lighter body. Both beers should be pitched with the same culture at the normal fermentation temperature for the given yeast culture. The goal here is not to produce two identical beers. It is to compare higher alcohol (hot flavors) and ester production between two different carbon to nitrogen ratios coupled with two different dissolved O2
Lager yeast strains can be divided into two groups, Saaz/Carlsberg and Frohberg. This division is based on the geographic heritage of the strains and was supported by molecular analyses of transposition distribution in these strains (24). Only recently, the differences in fermentation performance of these two groups were analyzed. It was shown that group I/Saaz yeasts are better adapted to low-temperature growth conditions (10°C), while group II/Frohberg yeasts ferment better at a higher temperature (22°C). Differences in sugar utilization became apparent, as group II yeasts utilize maltotriose and group I yeasts do not. Additionally, flavor differences were identified showing that Saaz strains produce several fold-lower levels of, e.g., isoamyl acetate (banana flavor) than Frohberg strains (25, 26).
What is interesting is that Saaz strains do not ferment maltotriose. They are also bigger producers of isoamyl acetate.
The MBAA recommendation is more than likely based on the fact that the American lager brewing industry was made possible by Emil Hansen generously sharing Carlsberg Unterhefe No. 1 (a.k.a. Sacchormyces Carlsbergensis) and the Carlsberg flask for pure culture propagation. The Midwestern brewing industry was built on Carlsberg Unterhefe No. 1, which lives on today as Miller's lager strain (a.k.a. Wyeast 2042 Danish Lager). Carlsberg Unterhefe No. 1 is the type strain for the Saaz family.