Escarpment labs Laerdal kveik optimum temperature and performance review

Fermentation performance and temperature preference of various Kveik yeasts has been one of the most common topics on this blog. We've shown kveik yeast are heterogeneous in their response to elevated temperatures (>30ºC); some seem to really prefer 'hot' temperatures (Voss, Hornindal) while some may not (Lutra). As far as we know, we were the first to show that the optimal fermentation temperature for Voss kveik (from Lallemand) is 37-38ºC and that temperatures >39ºC inhibit activity of Voss kveik.

My next project come out of an interesting observation from the Preiss et al (2018) paper in Frontiers. In Figure 4, Preiss and colleagues show the fermentation kinetics and final ethanol concentrations in small scale fermentations with 25 or so different kveik strains. Very importantly, they did the experiment at 1 temperature (30ºC) and measured the grams of CO2 produced every 24 hours for 3 days. In part B of Figure 4, Preiss and colleagues plot the grams of CO2 produced by all of the tested yeasts at 24 hours - this is essentially a rough proxy for fermentation speed, since they looked at which yeast produced the most CO2 before the end of the fermentations.

Interestingly, the fastest fermenter at 30ºC in their experiments was Laerdal kveik. This was astounding to me, because I know from previous experiments of my own that Voss kveik fully attenuates a 1.050 wort in less than 30 hours at the optimum temperature (37.5ºC). Is Laerdal kveik really faster? So I set out to determine the optimum fermentation temperature of Laerdal kveik from Escarpment using my 'standard method' to test yeast performance.

In this experiment I used the same exact recipe and process that I used for all of my previous kveik 'test' ferments, with one notable exception. Since I wanted to test 8 temperatures in triplicate (24 total fermentations), I chose to do 2.5 gallon batches so that I could do more replicates at one time (usually one triplicate at a time). I did this to save time (this experiment would only take 8 weeks to complete!) and reduce the total amount of beer I would have to drink.

**The figures/data in this blog post are also available in updated form in our preprint on kveik temperature adaptations: https://biorxiv.org/cgi/content/short/2021.06.15.448505v1

Here is my recipe and process.

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60% Pilsner malt

38% Vienna malt

2% Munich malt

Mashed at 65ºC for 1 hour, 78ºC mashout for 1 min, batch sparge

Mash pH of 5.45-5.5 to counteract kveik pH drop

OG 1.049

FG 1.012-1.025 (attenuation varied by temperature)

60 min boil

23 IBU Hallertau magnum at 60 min

1/4 a teaspoon wyeast nutrients at 10 min

0.7 IBU Hallertau Mittelfrueh at flameout

Chilled to 20ºC, 25ºC, 28ºC, 30ºC, 33.5ºC, 37ºC, 40ºC, 42ºC using immersion chiller

Aerated with a 5 micrometer stainless steel airstone (air) for 4 minutes

Pitch rate: 1 pack per 5 gallons (standard recommended pitching rate)

Fermented at the respective pitch temps: 20ºC, 25ºC, 28ºC, 30ºC, 33.5ºC, 37ºC, 40ºC, 42ºC.

I maintained temperature using a fridge fermentation chamber for my fermentation vessel coupled to an inkbird and heating pad. This allows temperature control of +/- 0.5ºC from 4ºC to 42ºC.

Once the fermentations finished (click here and go to the bottom to see how I calculate this), I transferred each beer to a corny keg and carbonated to 2.5 volumes.

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Figure 1: Fermentation kinetics for Laerdal kveik fermented in triplicate at 8 different temperatures (20ºC-42ºC)

The results from figure 1 are quite interesting. Fermentation begins rapidly after pitching with a 4-5 gravity point decrease in just the first 3 hours!! In shades of blue we have 20ºC to 30ºC, in green 33.5ºC, in yellow 37ºC, orange 40ºC, and red being 42ºC.

Starting with the coolest temperature, we can see that the performance at 20ºC is respectable, but it takes 4 days to reach full attenuation. The 25ºC incubation is much faster than 20ºC, but still looks nowhere near optimal. 28ºC, 30ºC, and 33.5ºC perform rather similarly, but it looks like 33.5ºC is fastest.

At 37ºC, we already see very significant inhibition of growth and fermentation in Laerdal kveik. The 37ºC treatment performs more poorly than the 25ºC. Reasonable attenuation is still possible at 40ºC, but Laerdal absolutely struggles and is massively inhibited at 42ºC.

However, the 28ºC treatment is the first to reach FG at 48.5 hours. At 30ºC, 33.5ºC, and 25ºC, it takes 72-73 hours to reach FG. This is very interesting. What does it mean? It means that the peak in fermentation performance is highest at 33.5ºC, but that 28ºC is better for overall performance. In fact, you're just as well off at 25ºC compared to 33.5ºC in terms of total fermentation time.

Figure 2: Effect of temperature on maximum fermentation activity in triplicate at 8 different temperatures (20ºC-42ºC) for Laerdal kveik

Figure 2 shows very clearly that the optimum temperature is around 33-34ºC for Laerdal kveik. The rates of fermentation drop quickly beyond 34ºC. However, keep in mind what I wrote above; the peak in performance is at 33.5ºC but the overall best performance is at 28ºC.

To me, it looks like Laerdal kveik may have a hard time fermenting maltose or maltotriose at high temperatures, since the rates are initially fast and rapidly drop off once approx. 60% of the attenuation is reached.

Figure 3: Effect of temperature on apparent attenuation in triplicate at 8 different temperatures (20ºC-42ºC) for Laerdal kveik

I did observe a very strong trend of decreasing apparent attenuation at higher temperatures for Laerdal. Apparent attenuation was at a solid 75% until 37ºC, where it dipped. All three replicates showed the same trend - the apparent attenuation was 73% at 37ºC, 71% at 40ºC, and only 48% at 42ºC. To be fair though, we can't trust the 42ºC results much because the yeast was so stressed.

Very cool is that the apparent attenuation started to decrease exactly where we saw temperature stress - anywhere above 34ºC.

Figure 4: Impact of fermentation temperature on sensory properties of Laerdal kveik (rating out of 5)

Now here is what brewers really care about: how do the beers actually taste? Unfortunately due to covid, it was not possible to do a tasting panel. Instead, my wife and I blindly tasted all of the beers and rated them. The figure above shows our average rating in 11 different sensory characteristics.

Keep in mind that this is our unique perception of the sensory properties and that you, or a panel, may have found slightly different results. I apologize for some seeming inconsistencies (for example, the 0 in 'body' at 28ºC). We really did these blind and so we didn't want to bias the results - that's just what we both happened to write down!

We got a lot of pineapple and apple esters (ethyl butyrate, ethyl caproate) at temperatures 37-40ºC. It tasted almost like apple juice at those temperatures! Escarpment labs also notes 'pineapple' as a major flavour.

So is Laerdal really much faster than Voss? The short answer is no, if you want to look at the max rates we saw with Voss kveik. The reason that Preiss et al (2018) observed a much faster rate of fermentation for Laerdal when compared to Voss is because their experimental temperature (30ºC) was very close to the temperature optimum for Laerdal (28ºC) but quite far from the temperature optimum for Voss (±38ºC). !!!!!

Conclusions:

1) Optimal overall fermentation performance for Laerdal kveik (Escarpment labs) was at 28ºC.

2) The fastest peak performance was at 33.5ºC.

3) Temperatures of 37ºC or higher inhibited fermentation. Temperatures above 40ºC severely restricted fermentation.

4) Laerdal kveik seems to be most fruity ('estery') at elevated temperatures - as one would expect. Ferment at 37-40ºC if you want pineapple and apple esters!

5) Laerdal kveik has the most 'kveiky' acidity at relatively low temperatures and may accentuate malts more at near optimum temperatures (30-33.5ºC)

References:

1) Preiss, R., Tyrawa, C., Krogerus, K., Garshol, L. M. & van der Merwe, G. Traditional Norwegian Kveik Are a Genetically Distinct Group of Domesticated Saccharomyces cerevisiae Brewing Yeasts. Front. Microbiol.9, 5412 (2018).