Brewer's Ed

Best Practices for Brewing with Thiolized Yeast

Our advice based on what we've learned so far

By Shana Solarte

Feb 17, 2023

Once you’ve covered the basics and understand what thiols are, the next step is optimizing your process, starting with your raw ingredients and recipe design. Thiol aromas can range from subtle to intense with a wide variety of tropical fruit flavors that can integrate into your beers, whether as a complement to a fragrant hop bill or a thiol-dominated aroma profile.

The best experiments change one variable at a time. We recommend starting with a tried and true recipe and substituting your yeast strain with a Thiolized strain. This will give you a baseline and help you think about how to modify your recipe based on the tips and guidelines below to enhance or minimize thiols.

Prominent thiols

To maximize thiol output, start at the very beginning: precursors. Load thiol precursors into the wort by mash hopping or even using grape-derived products that the yeast can later transform into free aromatics, especially when using Cosmic Punch. We have found hop varieties like Cascade, Saaz, Calypso, and Motueka to be especially helpful when mash hopping. Barley is also an abundant source of precursor — a 100% barley malt bill will yield more intense thiols than a grist incorporating wheat and oats, which have little to no precursors. 

Some hops, like Simcoe, Nelson Sauvin, Citra, and Mosaic have been found to have higher levels of free thiols, meaning that they will contribute some aromatic thiols to the beer on their own. This can translate as a tropical fruit aroma that can work alongside the thiol-releasing activity of the yeast to create a complex flavor profile.

From a process standpoint, heavy dry hopping can create intense hop aromas that compete with and may even overpower thiols. By easing up a bit on dry hopping rates, thiols can shine as the prominent aroma. Remember that thiols blend beautifully with hop aromas, but there are times when full-on thiol aromatics can be quite pleasant.

Precursor potential and barley terroir

While the research is still in progress, we have seen positive results when brewing with grain bills primarily comprised of malted barley. The actual amount of thiol precursor may vary among different species of barley as well as the extent to which they are malted. Equipped with this knowledge, brewers can begin to modulate their thiol output levels by altering the percentage of barley in the grist — brewing with increased amounts of wheat or oats, for example, will diminish the amount of thiol precursor available in the wort, which in turn will reduce the potential for stronger thiol aromatics in the finished beer. We’re hopeful that brewers and maltsters (and yeast labs, of course!) will continue to experiment with different grains and discover the full picture.

Integrated thiols

For the most part, keeping thiol levels from skyrocketing can be as easy as avoiding the processes that amplify them. Finding ways to blend thiols into the overall aroma profile as a complementary element can be rewarding and create a more complex beer — we recommend using yeast that gets its thiol-enhancing abilities from the yeast Irc7 enzyme (Cosmic Punch), which is less potent than those that use the highly active PatB enzyme from bacteria. Whereas using a mostly barley malt grist will provide the highest amount of thiol precursors, blending in wheat, oats, and even rice will reduce thiol potential. Skipping a mash hop and focusing more on whirlpool and dry hopping can further reduce the presence of thiols and integrate more hop aroma into the finished product. 

Another way to meld thiols with other beer flavors is by blending yeast strains. By fermenting with a 50/50 blend of Thiolized yeast and their corresponding parent strains, you can expect about the same reduction in thiols in the finished beer. Blending 25% Thiolized yeast with 75% non-Thiolized yeast would yield about a quarter of the thiols compared with a 100% Thiolized yeast, and so on. 

When running your own trials, start with the non-Thiolized parent strain (e.g., try British V before Helio Gazer) and see how the finished beer might benefit from some extra tropical aromas. You can even get into combining beers to figure out the balance you like best before experimenting with yeast blends. We suggest blending dry hopped beer with a Thiolized lager and tasting it at different ratios. With this method you can really dial in the balance between hops and thiols and find the exact point when thiols begin to punch through that rich dry hop aroma.

Go beyond hoppy beers with Thiolized yeast. Try layering thiols into styles where fruit drives the flavor profile, like fruited IPAs, sours, or even smoothie sours. An extra component of thiol-derived fruitiness could take any of these styles into uncharted territory and find some new fans. The most important consideration for thiol integration is up to you — build your recipe around the thiol intensity that you seek.

We’ve only scratched the surface when it comes to what’s possible with thiol-enhancing yeast. Experimenting should be fun! Take a scientific approach, changing just one variable at a time to truly understand how each change affects the outcome, and find the flavors that really suit your beer.

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