[Beer Lecture] Chapter 7. The Cold of Alpine Caves
Historical period: 15 century CE
Scene of action: Bavaria
Let’s now discuss another vital beer ingredient: yeasts. Without them, you can’t brew beer, make wine, or bake bread — which means they were in some sense ‘domesticated’ several thousand years ago. That makes the fact that we actually know very little about yeast domestication even more surprising.
We are now aware of more than 1500 yeast species. And when humanity started learning brewing, wine-making, and baking, many different ‘wild’ yeast kinds were used for leaving.
However, at the end of the 19th century when microbiologists began to study yeasts, it turned out that winemakers and bakers were using one very specific species: Saccharomyces cerevisiae, or simply ‘baker’s yeast’. How exactly did humans isolate that specific yeast from the broad spectrum of wild species is right now quite unclear. We don’t even know whether our ancestors found S. cerevisiae in the wild, or bred it, and when this actually happened. The latest research demonstrates that quite probably S. cerevisiae was first isolated during the industrial revolution in brewing, e.g. relatively recently[1].
But instead, we rather well know the history of another yeast species used by brewers, S. pastorianus. It was actually bred by humans as a result of the hybridization of the above-mentioned S. cerevisiae and ‘wild’ S. eubayanus[2] presumably in the 15th century CE in Bavaria. In those times brewers were struggling with beer spoilage and unpleasant odors, and low temperature helped with both. In their determination to produce better beer Bavarian brewers (probably, monks of the secluded monasteries[3]) began to keep their beer in the cold of Alpine caves, just several degrees above zero Celsius — and bred new yeast species. Traditionally, beer was left to ferment at room temperature (around 20 Celsius) for several days; a new Bavarian technique implied a prolonged fermentation period (roughly 3 weeks) and then storing beer at 5–10° Celsius for an even longer period of time. This new type of beer was called ‘lager’, meaning ‘to store’ in German. A ‘lagerization’ as a specific brewers’ activity was first mentioned in 1420 CE. However, it was not widespread until the 60s years of the 19 century, because of obvious reasons: the technology required a huge amount of ice to be used[4].
How to taste
First lagers were still dark beer (and remained as such up until the 20th century), so the most authentic ones are contemporary German dark lagers (so-called dunkelbier) or German bockbier, which is being produced utilizing the lager technology. You may take any dunkel: in fact, that’s quite common modern dark beer. The most praised examples of the style are Ayinger and Andechser, though for a full submersion you might try to find Weltenburger (the brewery at the Weltenburg Abbey was founded in 1050 and is considered to be one of the oldest in the world) or Spaten Dunkel (which is produced since the 14th century).
The taste and the temperature
Yeast kind defines not only the rapidity and the temperature of the fermentation but also how the process looks like. Baker’s yeast ferments intensively, forming a think foam at the tank’s surface which brewers often used as a starter for the next brew. At the same time, lager yeast behaves calmly, doesn’t produce a lot of foam, and sinks to the bottom of the vessel. That’s why corresponding beverages are colloquially called ‘top-fermented’ and ‘bottom-fermented’ beers respectively — though brewers had long ago developed baker’s yeast strains that sank to the bottom as well. The ‘high-temperature fermentation’ (or ‘warm-’) and ‘low-temperature fermentation’ terms would describe the situation much more adequately but regretfully see rare use.
For high-temperature fermented beers, the word ‘ale’ is now used almost universally (which has exactly zero historical justification), and the S. cerevisiae yeast is likewise dubbed ‘ale yeast’. In this book, we use the word ‘ale’ only for beverages that were called ales at the time they originated, and not for denoting yeast species. If such an indication is needed, in this book it’s always explicit. Other yeast species used by brewers (of Brettanomyces genus, for instance) are also considered ‘top-fermenting’.
The difference between high-temperature fermentation and low-temperature one is that chemical reactions happen more turbulently at higher temperatures and enrich beer with complex ethers that are responsible for the flavors of bananas, raisins, berries, etc. Low-temperature beer will have a more accentuated ‘bread-like’ profile and comprise fewer tinges in its taste and aroma. Interestingly, lager yeast might be forced to ferment at higher temperatures; the resulting beverage is called steambeer.
This is Chapter 6 of my book on beer and brewing history. The work continues on Github.
References
- 1 Gallone, B., Mertens, S., Gordon, J. L., Maere, S., Verstrepen, K., Steensels, J. (2017), p. 149
- 2 ibid, p. 151
- 3 Jackson, M. The birth of lager
http://www.beerhunter.com/documents/19133-000255.html - 4 Meussdoerffer, F. G. (2009), p. 28