Brew With Us ESSENTIALS – phenolic yeasts and kveik

Posted on 23rd June 2022

Ester and the Phenols, LIVE!

We’ve looked at “clean” yeasts that work well across lots of ale and lager styles.

Now we’ll delve into specialty yeasts – and we’ll meet our friend “Ester”.

Okay, an Ester is actually a chemical, not a person, but they’re definitely our friend when it comes to yeast flavour. Esters are one class among many of the flavour compounds produced by yeast, and are typically described as floral and fruity. Yeasts that produce lots of esters can often complement hops.

Phenols are another major class of flavour compounds, and these are typically described as peppery, clove-like, and spicy. Phenolic flavours aren’t always welcome in “clean” ales and lagers, but they are the signature of Belgian ales. Blonde, dubbel, tripel, and saison all get their special, peppery snap from yeast phenols.

  • Wyeast 3724 “Belgian Saison”
  • White Labs WLP565 “Belgian Saison I”
  • Omega OYL-027 “Belgian Saison I”
  • Fermentum Mobile FM27 “Seasons Greetings”
  • Lallemand “Belle Saison”
  • NBS Belgian Saison

Earthy, spicy yeast notes in the classic saison style.

  • Wyeast 1214 “Belgian Abbey Style Ale”
  • White Labs WLP500 “Monastery (Belgian Abbey) Ale”
  • Imperial B63 “Monastic”
  • Omega OYL-018 “Abbey C”
  • Fermentum Mobile FM25 “Monastery Meditation”
  • Safbrew T-58

Produces fruity esters that work well in darker “Abbey” style ales.

  • Wyeast 3787 “Belgian High Gravity”
  • White Labs WLP530 “Abbey Ale”
  • Imperial B48 “Triple Double”
  • Omega OYL-028 “Belgian Ale W”
  • Fermentum Mobile FM27 “Abbey Artefacts”

Fruity esters balanced with spicy phenols. Tolerates high levels of alcohol (up to 15% ABV).

  • Wyeast 1388 “Belgian Strong Ale”
  • White Labs WLP570 “Belgian Golden Ale”
  • Omega OYL-019 “Belgian Ale D”
  • Mangrove Jack’s M31

Fruity and phenolic, very high attenuation means it finishes very dry.

The yeasts used for wheat beers – both Belgian wit and German weizen styles – also produce large amounts of both esters and phenols. These are used to quite different effects. In wit, fruit esters and peppery, herbal phenols complement and accentuate the spices and herbs added to make the characteristic perfumed aroma and flavour. In weizen, aka Weissbier, the signature flavours of bananas and cloves come solely from the yeast: the banana is an ester (isoamyl acetate, to get technical), and the cloves are a phenol (guaiacol), which the yeast produces from ferulic acid, which is found in wheat.

The amount of phenols a yeast produces is closely linked to the type of sugars in the wort – i.e. what was in your grain bill and how you mashed it. And yeast tends to produce more esters at warmer temperatures (and less when it ferments cooler). So by adjusting your recipe and fermentation temperature, you can get the balance of phenols and esters you prefer. Remember that almost all yeasts produce esters, but most “clean” yeasts don’t produce the kind of spicy and herbal phenols found in Belgian and wheat beers. We’ll cover more on controlling fermentation temperature in a later chapter!

  • Wyeast 3944 “Belgian Witbier”
  • White Labs WLP400 “Belgian Wit”
  • Imperial B44 “Whiteout”
  • Omega OYL-030 “Wit”
  • Fermentum Mobile FM20 “White Wellingtons”
  • Mangrove Jack’s M21

A classic Witbier yeast. Spicy, herbal phenols, fruity esters, and a slightly tart finish.

  • Wyeast 3068 “Weihenstephan Weizen”
  • White Labs WLP300 “Hefeweizen Ale”
  • Imperial G01 “Stefon”
  • Omega OYL-021 “Hefeweizen Ale I”
  • Fermentum Mobile FM41 “Cloves and Bananas”
  • Safale WB-06

A classic Weizen yeast! Balanced towards banana esters with clove-like phenols emphasised at lower fermentation temperatures.

Time to Kveik

A few years ago, the ideal of fermenting beer at temperatures upwards of 30°C would have you laughed out of many brewing discussions. The flavours produced by “clean” yeasts at those levels would be almost undrinkable! Then word began to spread about kveik: yeasts that not only prefer things hot, they produce their best flavours there too.

Kveik cultures (say “k-vike” or “k-vake”) are blends of multiple yeast strains, sometimes including bacteria, that have been passed down through generations of farmhouse brewers in Norway. Over time a lot of original cultures were lost as brewers moved to using purified single cultures (like most of the strains we’ve discussed so far), until a few years ago when beer historians began efforts to preserve the original kveiks. You can read more about both kveik and farmhouse brewing in Lars Garshol’s excellent book, Historical Brewing Techniques.

The special thing about kveiks is that they have evolved to cope with conditions that would kill regular brewing yeasts outright. Many kveiks can survive drying without special equipment, and some can survive freezing! Added to that, they typically prefer fermenting at temperatures between 30-37°C, and many will finish in under 72 hours. Naturally, these characteristics have got brewers very interested.

It’s important to note that kveiks are not a single strain, but a family of yeasts from a similar region. Some are very different in behaviour as well as flavour, so there is no single “kveik” flavour or character. There’s also no beer style called “kveik”: these yeasts are traditionally used to make a wide variety of styles.

Many kveiks are named after the area they were found or the farmhouse brewers who preserved them. For example, Voss and Hornindal are regions in Norway. Interest in kveik has led to other farmhouse yeast cultures being sought out and preserved, including strains from Lithuania and Latvia. These are often referred to as kveiks, though technically kveik – literally the Norwegian word for yeast – refers only to cultures from Norway.

There’s a lot of research going on into what makes kveiks so different. Most kveik cultures are blends of Saccharomyces cerevisiae, the same species used elsewhere in brewing. Blends can be unstable, with the proportions changing over time, so most commercially available kveiks are single strains isolated from the original blends. These “isolates” still have kveik’s special properties, but are easier for yeast labs to grow and replicate.

Kveik ring
  • Imperial A43 “Loki”
  • Omega OYL-061 “Voss Kveik”
  • Fermentum Mobile FM53 “Voss Kveik”
  • The Yeast Bay WLP4045 “Sigmund’s Voss Kveik”
  • WHC “Ragnar”
  • Lallemand “Voss”

Originally collected from Sigmund Gjernes, a farmhouse brewer in the Voss region. Earthy, Christmas spices, but most prominently orange peel and citrus.

  • Omega OYL-091 “Hornindal Kveik”
  • WHC “Bjorn”
  • Bootleg Biology “Aurora”
  • Escarpment “Hornindal Kveik Blend” (two Sacc strains, no bacteria)

Originally a blend of eight strains including some bacteria, producing a unique “milky caramel with mushroom” flavour. Commercial versions listed here are single strain isolates with a pronounced tropical fruit flavour.

Lutra kveik

Many kveiks will happily ferment at “normal” temperatures of 20°C, though they will often produce very little of their signature esters and flavours this “cold”. Because they are much more neutral flavoured at these temperatures, it’s possible to use kveik to produce lagers without the need to cool your fermenter down to 10°C or under. Dedicated lager strains developed from kveiks are now available, such as “Lutra” from Omega and “Krispy” from Escarpment. More novel and interesting types of yeast developed from kveiks are sure to become available over the coming years – watch this space…

A day (or more) in the life of yeast

More like a few weeks… it’s fermentation time!

From pitching rates to temperature control, next we’ll cover everything you need to know to get the right flavours from your chosen yeast!

All content © The Malt Miller 2022

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