Best yeasts to use when brewing lager beers

Monday, October 6, 2025

The Brewer's Guide to Lager Yeast: 

Patience, precision, and an understanding of yeast science are the keys to a world-class lager. Here's your complete guide.

The production of a truly brilliant lager is often seen as the pinnacle of brewing. Unlike the boisterous, forgiving nature of an ale, a lager offers nowhere to hide flaws. 

Its clean, crisp character is a testament to precision and patience. The heart and soul of this process is the unique yeast that not only tolerates the cold but thrives in it, producing a flavor profile of unparalleled subtlety and smoothness.

The most commonly used lager yeast strains, belonging to the species Saccharomyces pastorianus, are a different breed entirely from their ale-producing cousins. 

This guide delves into the science of these cold-loving organisms, introduces you to the classic strains, and provides a step-by-step protocol for mastering the art of the cold ferment.

Part 1: The Genetic Divide — Ale vs. Lager Yeast

A Tale of Two Species: Top vs. Bottom Fermenting

The fundamental difference lies in their genetics. Ale yeasts (Saccharomyces cerevisiae) are "top-fermenting," meaning they form a thick layer of yeast (krausen) at the top of the fermenter and prefer warmer temperatures (60-75°F / 15-24°C). Lager yeasts (S. pastorianus) are "bottom-fermenting," working slowly at the bottom of the vessel at much colder temperatures (45-55°F / 7-13°C).

Master Brewer Tip: The Hybrid Origins of Lager Yeast

Saccharomyces pastorianus is a fascinating natural hybrid. Genetic sequencing has revealed it's a cross between the common ale yeast, S. cerevisiae, and a wild, cold-tolerant species, Saccharomyces eubayanus. 

This unique genetic heritage gave it the ability to thrive in the cold caves where Bavarian monks first lagered their beers centuries ago. 

It also gave it the ability to ferment more complex sugars, resulting in a drier, crisper final product.

This cold fermentation is the key to a lager's signature flavor profile. The lower temperatures suppress the production of fruity esters and spicy phenolics that are characteristic of ales. 

Instead, lager yeasts can produce more sulfur compounds, which, while initially pungent, dissipate during the long cold-conditioning phase (lagering), leaving behind an exceptionally clean and crisp beer.

Part 2: Choosing Your Workhorse — A Guide to Classic Lager Strains

The Brewer's Roster: Strain Profiles

Selecting the right yeast strain is critical for hitting your target flavor profile. Here are some of the most popular and reliable workhorses in the brewing world.

W-34/70 (Saflager W-34/70)

Origin: The legendary Weihenstephan strain from Germany. Arguably the most popular lager yeast in the world.
Profile: Exceptionally clean, crisp, and malty. Allows malt and hop character to shine through with a neutral flavor profile.
Best For: Everything. German Pilsners, Helles, Bocks, Oktoberfests. This is the ultimate all-rounder.

S-23

Origin: VLB-Berlin. A popular choice for West European style lagers.
Profile: Produces slightly more fruity esters than W-34/70, especially when fermented at the higher end of its range. Finishes very dry.
Best For: Fruity lagers, Dortmunder Export, and American-style Pilsners.

S-189

Origin: Hürlimann brewery in Switzerland.
Profile: A very neutral fermenter that enhances maltiness and body. Low sulfur production.
Best For: Traditional European lagers where a rich, malty character is desired, like Bocks and Dunkels.

Part 3: The Art of the Cold — A Step-by-Step Lager Fermentation Protocol

From Pitch to Pour: The Four Critical Phases

A successful lager fermentation is a carefully controlled process. Rushing any step will lead to off-flavors that have nowhere to hide in the finished beer.

  1. Phase 1: Pitching Rate & Oxygenation. Because of the cold, slow fermentation, you need to pitch roughly double the amount of yeast you would for an ale. For liquid yeast, this means making a large starter. For dry yeast, it means pitching two packets. Oxygenate your chilled wort thoroughly before pitching; yeast needs oxygen for a healthy growth phase.
  2. Phase 2: Primary Fermentation. Pitch your yeast into the wort once it's chilled to your target temperature (typically 48-55°F / 9-13°C). Maintain this temperature steadily for 1-2 weeks, or until fermentation is about 75% complete. This is where the clean flavor profile is developed.
  3. Phase 3: The Diacetyl Rest (The Pro Move). This is the most critical step for avoiding a common lager off-flavor (diacetyl), which tastes like butter or butterscotch. As fermentation slows, allow the temperature of the beer to free-rise to 60-65°F (15-18°C) for 2-3 days. This encourages the yeast to "clean up" after itself, reabsorbing the diacetyl precursors it produced during primary fermentation.
  4. Phase 4: Lagering (Cold Conditioning). After the diacetyl rest, slowly lower the temperature by a few degrees each day until you reach near-freezing (32-38°F / 0-3°C). Let the beer condition at this temperature for at least 4 weeks, and up to several months. This is where the magic happens: sulfur compounds dissipate, yeast and proteins drop out of suspension, and the beer develops its signature smooth, clean, refined character.

Earning Your Stripes

Brewing a world-class lager is a journey of patience and precision. It requires careful temperature control and a deep respect for the unique needs of your yeast. 

By understanding the science behind the strains and mastering the four phases of fermentation, you're not just brewing beer - you're crafting a masterpiece. 

Embrace the cold, give your yeast the time it needs, and you'll be rewarded with a pint of unparalleled clarity and crispness.

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