species
Saccharomyces pastorianus
The cold-fermenting hybrid species behind all lager, producing very little ester or phenol character and leaving malt and hops exposed.
Pastorianus is a natural hybrid of Saccharomyces cerevisiae and the cold-tolerant Saccharomyces eubayanus, which was only identified in the wild in 2011 — in Patagonia, far from any European brewery. How it reached Bavarian cellars remains genuinely unresolved.
It ferments at 7–13 °C, settles out rather than rising, and can ferment melibiose, which cerevisiae cannot. Cold fermentation suppresses ester and phenol formation, which is the whole reason lager tastes the way it does.
It also produces more sulphur compounds than ale yeast during fermentation; extended cold conditioning is partly what clears them.
Behaviour
| Scientific name | Saccharomyces pastorianus |
|---|---|
| Fermentation temperature | 7–13°C |
| Apparent attenuation | 72–85% |
| Flocculation | medium |
| Esters | low |
| Phenols | none |
Used in
- International pale lager
The global mainstream lager: pale, clean, lightly hopped and built for consistency and refreshment above flavour intensity.
- American lager
A very light, highly attenuated pale lager brewed with a substantial proportion of maize or rice, prioritising drinkability and cold service.
- Czech pale lager
The Czech everyday lager: lower in strength than the premium version but keeping the soft bready malt and generous Saaz hopping.
- International amber lager
A light, commercially-produced amber lager, most familiar in its Mexican form, with gentle caramel over a crisp body.
- International dark lager
A commercially-produced dark lager, light in body and gently sweet, with colour contributing more than flavour.
- Pre-Prohibition lager
A reconstruction of the American lager brewed before Prohibition: fuller, more bitter and more characterful than what replaced it.
- Cold IPA
A lean, dry IPA fermented with lager yeast at higher temperature, using maize or rice to strip body and expose hop aroma.
- Alcohol-free pale lager
A pale lager produced at or near zero alcohol, now the largest and most refined part of the no-alcohol category.
Evidence
What BeerHQ knows about this, and how. Every statement carries the state of the evidence behind it rather than being presented flatly as fact.
Emil Christian Hansen’s isolation of a single pure yeast strain at Carlsberg in 1883 made reproducible lager fermentation possible and was shared rather than patented, which is why it spread across the industry quickly.
Backed by a source
Sources: Beer: The Story of the Pint — print; Yeast: The Practical Guide to Beer Fermentation — print
Saccharomyces pastorianus is a hybrid of S. cerevisiae and the cold-tolerant S. eubayanus, the latter of which was not identified in the wild until 2011, in Patagonia.
Backed by a source
Sources: Journal of the Institute of Brewing; Yeast: The Practical Guide to Beer Fermentation — print