Lagers or Lager beers offer a class of beers offering a world of flavours and diversity beyond common knowledge. Most consumers are familiar with relatively neutral, pale, medium alcohol level crystal clear and mildly bitter versions. However, there are a vast range of flavours within the lager category.
Pale lagers are often considered to be the most drinkable and therefore the most consumed all around the world, alongside regional variations and very strong branding. But lager beers exhibit a wide variation of characteristics comparable to ale beers, including colour, hoppiness, maltiness, bitterness levels, body, etc.
Amongst the most traditional parameters of lagers are the fermented flavour, which tend to be less intense over time. This parameter changes with new craft lagers, and it is a direct consequence of the chosen yeast and fermentation process.
What defines lager beer?
If its not solely flavour characteristics that define what lager beer is, what does? The answer lies with the yeast species used to ferment it. While ale beers are fermented with a wide range of Saccharomyces cerevisiae (S. cerevisiae) strains, lager beers are fermented with Saccharomyces Pastorianus (S. pasteorianus) a bottom fementing yeast.
Bottom fermentation is often used to describe lager fermentation. Our ancestors, without understanding the phenomenon, used to collect yeast from the top of the fermenters. During so, a specific phenotype that rises at the end of the fermentation was selected: top fermentation (ale yeast). To the contrary, lager yeast is defined by another phenotype; yeast that settle at the bottom of the fermenter.
It is worth noting, however, that today this distinction does not necessarily hold true due to advancements in brewing techniques and yeast management.
Lager yeast is relatively recent in evolutionary history compared to S. cerevisiae. With traces of fermented grain dating over 10,000 years s.cerevisiae has been part of the human diet for millennia. As a result, numerous domestication events allowed its phenotypes to evolve. Amongst others, maltotriose utilization has been increased and phenol production both being important and differential flavour aspects to lagers.
S.pastorianus is actually a hybrid yeast.
For a significant period, one only parent of this hydbrid was known: S.cerevisiae. More recently the puzzle was solved with the discovery of Saccharomyces eubayauns; the second parent according to today’s microbial evolution theory.
While the exact details of the hybridization event remain uncertain, extensive research has shed light on the process. Most likely, the new hybridwas born when S.cerevisiae and S.eubayanus bred in a brewery environment. A plausible scenario suggests that the breeding may have taken place during fermentation in the cold caves of Bavaria during the 15th century.
Cryotolereance which is the ability to maintain physiological and genetic stability at low temperatures, played a significant role in the selection of the lager yeast species. Lager yeast was favoured for its capacity to ferment at low temperatures, unlike ale yeast, which struggles to complete fermentation below 16 – 18⁰C.
Lager yeast can effectively achieve final attenuation at temperatures lower than 11⁰C. In the Czech Republic its not uncommon to transfer beer into maturation tanks when around 3 – 4 ⁰C (when attenuation has only reached 73-75%.) This extended fermentation process may take an additional three months but it will not stop until it’s over.
Lager trials in the Fermentis Academy technical hall (Photo: Fermentis)
Apart from being cryotolerant, the S.pastorianus yeast strain exhibits characteristics such as medium- high attenuation, good flocculation and sedimentation properties, alongside being phenolic off flavour (POF negative).
Compared with ale yeast, lager strains have lower genetic diversity.
Lastly, lager yeast is known, apart from exceptions, to be very neutral in its fermentation flavour formation. S.pastorianus does not produce noticeable amounts of higher alcohol (fusal alcohols) and fruity esters compared with S.cerevisiae. But what is neutral in beer? A brewmaster can make the perfect wort in the brewhouse however, the wort produced will not be a tasty beverage. Wort is heavy, not refreshing and full of undesirable aldehydes.
Only a beer yeast can remove the aldehydes and increase the freshness and drinkability in a word – make it a good beer.
To the end, lager beer is not neutral at all (nor is an ale yeast). Lager yeast reveals the hidden potential of the raw material used and unveils all the effort of the brewmaster who has worked so hard to make the perfect beer.
Diversity in lager beer styles
When thinking about the vast diversity of lager beer, one common feature comes to mind: balance. Unlike certain modern versions of craft and ale beers, the soul of most lagers is finding the perfect equilibrium between bitterness, sweetness, drinkability, malt character and fermentation flavours.
Finding the perfect strain for each beer style alongside brewery specificity is of major importance. Pilsner is the most iconic style of what is considered a premium lager. A Pilsner typically offers a crisp and refreshing tasted with moderate to high bitterness, balanced hoppy notes, subtle maltiness and a clean dry finish. Fermentation flavour is neutral, just revealing the combination of raw materials used to make the beer.
Fermentis provides ideal solutions for these styles with yeasts such as SafLager™ S-23 and SafLager™ W-34/70 which can ensure neutral character avoid off flavours.
Marzen Beer, Octoberfest or Vienna lagers are variations of similar styles. From strong golden colour to copper, they are characterized by their rich maltiness, balanced by a clean finish and moderate hop bitterness.
These styles showcase a robust malt profile with flavours of toasted bread, caramel and toffee, balanced by a moderate hop bitterness and clean, dry finish, making them ideal choices for autumnal festivities and cool weather enjoyment.
Of German origin, SafLager ™ W-34/70 allows a clean fermentation profile to the benefit of the malty character of Marzen, Octoberfest or Vienna lager beers.
For slightly fruiter versions, SafLager™ S-23 remains an ideal option tht can certainly add a layer of complexity to some malty-fruitiness that can be present in these styles.
In General, fruitiness is a flavour often enjoyed by consumers and some brewers are diversifying lagers in this regard. Often called estery lager, it is an alternative to the neutral fermentation flavour of S. pastorianus.
Although every brewery yeast produces higher alcohols and esters (even in bottom fermentation), in most cases, these volatiles are close or below their respective flavour thresholds. One of the most important features is the ratio of higher alcohol to esters. A common target to reach for values between 3 and 4 and 1.
Fermentis SafLager™ E-30 produces significantly higher amounts of fruity esters, specifically isomyl -acetates, that provide a banana like character to beer, at least two times more than any other lager yeast in the Fermentis range. This yeast allows for innovative alternatives to classic and modern lager beer styles bringing forward the fermentation fruitiness and adding extra layers of flavour complexity.
Modern advancements are not limited to fermentative and malty flavour diversity, they also encompass the development of new hop nuances. Apart from the traditional and hopped Pilsners, Italian lagers are dry-hopped versions, using the same noble European hop (Saaz, hallertau Mittlefruh, Tattenang Spalt, etc.). The base of the beer is very similar to Pilsner styles with a balance leaning towards hops having medium to high bitterness, freshness and lower malt character. The dry hopping adds to the complexity of the beer providing extra layers of floral and herbal notes and the yeast choice can make a difference.
The perfect yeast to allow for noble hop expression is SafLager™ S-189. Cold IPA, New Zealand Lager or India Pale Lagers are variations of the lager version of IPA. Characterised by its high hop dosage, a medium to high smooth bitterness, these beer styles add diversity and are a result of the brewers creativity. Any variety of hop can be used for dry and late hopping to confer a wide range of fruity notes such as citrus, tropical floral or herbal.
In conclusion, lager beers present a rich spectrum of flavour profile and styles, each possessing its own distinct character. While malts and hops often take the spotlight, its essential not to overlook the crucial role of yeast.
The craftsmanship of the brewmaster in harnessing these elements renders lager beer a timeless classic and a beloved choice of beer for beer enthusiasts worldwide.
Authors: Gilles Goemaere (Techincal Support Mananger – Europe, Fermentis) & Gabriela Montandon, PhD (Fermentis Academy Sensory Analysis Manager)
Fermentis offers a wide range of SafLager™ yeasts to suit varying lager flavour profiles (Photo: Fermentis)
