The Right Yeast for Homebrewing Clean Lagers

There is always a perfect moment for a lager: a hot summer day, a game night, the end of a long working day, or a light lunch — to name just a few perfect moments! One of the cruelest paradoxes of homebrewing is that summer is the best time to drink a light lager. However, this beer style can’t be brewed properly in the summer unless you have access to fermentation temperature control, which most homebrewers do not. Historically, lagers were brewed in the cooler months and then stored in caves for a long, cold maturation period called “lagering.” Alas, most homebrewers also lack access to lagering caves. Thus, many homebrewers resign themselves to drinking commercial lagers during the summer until the cooler temperatures return. 

What is lager yeast? 

A lager, by definition, needs to be brewed with lager yeast of the species Saccharomyces pastorianus. The S. pastorianus yeasts are hybrids of S. cerevisiae ale yeast with S. eubayanus, a cold-tolerant yeast species. The optimal fermentation temperature range for different types of lager yeasts is determined by genetics. Of the two traditional lager yeast lineages, Group I (Saaz) strains have more DNA from S. eubayanus and ferment at cooler temperatures (8-12°C), whereas Group II (Frohberg) strains have equal DNA from S. eubayanus and S. cerevisiae and ferment slightly warmer (10-15°C). Virtually all commercial lager strains today are Group II.

A few years ago, yeast scientists used non-GMO breeding methods to select a novel lineage of lager yeasts. These Group III strains have a broader temperature tolerance because they have more DNA from S. cerevisiae. The first commercial Group III lager yeast is LalBrew NovaLager™, which has a wider optimal temperature range of 10-20°C. 

Why is brewing lager at home a challenge? 

The delicate, clean, and balanced flavor profile of a lager is achieved by fermenting at lower temperatures with traditional Group I or II strains. This keeps ester levels lower and reduces the formation of off-flavors such as H₂S (rotten eggs). For traditional lager strains, warmer fermentation temperatures tend to promote higher H₂S levels. H₂S will generally be reabsorbed by the yeast during the maturation period after fermentation is complete. 

Diacetyl is another common off-flavor in lagers. Yeast secretes diacetyl precursors into the beer during fermentation, and diacetyl is re-absorbed by normal yeast metabolism after fermentation is complete. Diacetyl reabsorption is slower at these low temperatures, so a diacetyl rest is normally performed by increasing the temperature slightly at the end of fermentation. Diacetyl is produced in greater amounts when valine levels are limited, and traditional lager yeasts tend to produce more diacetyl since they do not uptake valine efficiently. 

Refreshing lagers brewed at home with LalBrew NovaLager™ 

The ability to ferment warmer with Type III strains is a huge benefit for homebrewers since no diacetyl rest is required. LalBrew NovaLager™ will not produce H₂S since it lacks a gene for sulfur metabolism. Furthermore, LalBrew NovaLager™ has a greater amount of S. cerevisiae DNA, meaning it efficiently uptakes valine from the wort and produces lower levels of diacetyl compared to traditional lager strains. Clean and neutral flavors are consistently reported when fermenting LalBrew NovaLager™ throughout the temperature range of 10-20°C. A few brewers have even pushed the limits above 25°C with great results (some intentionally, others due to glycol failure). 

With LalBrew NovaLager™, it is possible to brew crisp and clean lagers in the heat of the summer without the need for refrigerated fermentation control. No need to purchase refrigeration equipment, no need to do a diacetyl rest, and little to no maturation required to reduce off-flavors. You can focus more on relaxing with your lager in the sun with a simpler process, less equipment required, and less energy required for extended cold maturation. Refreshing!