Guide To Thiolised Yeast (2024)

WHITE LABS YEAST OMEGA YEAST MASH HOPPING

STAN HIERONYMUS
The Complex Case of Thiols

Thiols, also known as mercaptans, are sulfur-containing organic compounds with a sulfur atom bound to a hydrogen atom. Thiols make up less than 1% of the essential oils in a hops cone but might hold a key to the fashionable in-demand tropical flavors.

Waiting for technology that turns brewing research into information useful to brewers can feel a little like waiting for a flying car. At the International Brewers Symposium on Hop Flavor and Aroma in Beer last summer at Oregon State University, five of the dozen presentations emphasized the role thiols play in creating the bold, often tropical, flavors currently fashionable in beer. Scientists in France, Belgium, Japan, the United States, and Germany are all involved in related research.

The potential seems so obvious that Nyséos, a specialty laboratory in France that focuses primarily on wine, has created a Thiol Potency (TP) indicator. Laurent Dagan, director at Nyséos, explains that discoveries about the role thiols play in developing flavor and the TP indicator are his “call” to brewers. “Hey, we have new information. It is complex, but we are trying to find indicators useful for you. What do you think about that?” he asks. The key word is complex because thiols make up less than 1 percent of the essential oils in a hops cone, and there are uncounted hundreds of compounds that contribute to hops odor that our brains convert into hops aroma.

What Are Thiols?
Thiols, also known as mercaptans, are sulfur-containing organic compounds with a sulfur atom bound to a hydrogen atom. Scientists first identified them in hops in the early 2000s, focusing on three that winemakers have known about for decades. One, 4-mercapto-4-methylpentant-2-one (4MMP), smells and tastes of box tree, black currant, and ribes. It is also known as 4-methyl-4-sulfanylpentan-2-one (4MSP). Another, 3-mercaptohexan-1-ol (3MH), is often described as exotic, smelling of rhubarb and citrus. And the third, 3-mercaptohexyl acetate (3MHA), is reminiscent of passion fruit and guava.

These compounds are all prominent in Sauvignon blanc, Riesling, and other wines, although they do not occur in grapes. They are formed during fermentation from precursors present in grape must. However, free thiols have been identified in many hops varieties along with two different bound forms (precursors) in both hops and barley malt. “Little is known about how these analytes develop in malt and hops over time or what process changes directly result in the increase of these analytes,” says Scott Lafontaine, a graduate research assistant at Oregon State University. Included are not only the thiols found in wine, but several others.

Analyzing thiols is challenging because of their low concentration and high reactivity. The standards and instrumentation that are needed to measure them are very expensive, and few laboratories have the equipment needed. “Part of the reason [this is challenging] is that thiols have very low odor-detection thresholds, and therefore, very small concentrations of these analytes can potentially have a large impact on beer flavor,” Lafontaine says. “In terms of concentrations, we are looking at parts per trillion. To give you an idea of what we are trying to find, it is like looking for the top of a pin in an Olympic-size swimming pool.”

Whoa, There’s Never a Single Marker
Stop and take a breath. Thiols are not a magic bullet for creating tropical flavors. The hops aroma/flavor matrix remains a product of synergy. Remember the lesson learned with linalool, a monoterpene. In 1981, Val Peaco*ck and associates at Oregon State had suggested the importance of linalool to hops aroma. They developed a model to predict the amount of floral-hops aroma likely in a beer based on the amount of linalool, geraniol, and geranyl esters in the essential oils. This led to research by other scientists. Peaco*ck noticed that “because of the amount of attention given to linalool during recent decades, its perceived importance has been elevated far beyond its true relevance.” As a result, he concluded, “this distorts brewers’ understanding of the nature of hops aroma in beer. Hops have more to contribute to the aroma of beer than just linalool.”

Thiols in Action
As reported in “Hops Oils & Aroma: Uncharted Waters” (Craft Beer & Brewing Magazine®, March/April 2016), a team at Sapporo Breweries in Japan conducted a study in 2012 in which they compared the compositions of monoterpene alcohols in various hops, examining the behavior of geraniol and citronellol under various hopping and hops-blend conditions. Among other things, their experiments demonstrated that the co-existence of linalool, geraniol, and citronellol could increase the perception of “citrus” in a model solution. Anecdotally, using this information, adventurous brewers combined hops high in linalool (such as Bravo or Nugget) with others rich in geraniol (for instance, Chinook) to brew beers they described as fruity, sometimes tropical. But it turns out linalool, geraniol, and citronellol may not have been totally responsible for those flavors.

Following additional research, the team from Sapporo has a new hypothesis. In their experiments, sensory panelists rated various aroma attributes of a solution dosed with 4MMP, scoring it two (out of four) for “tropical.” Similarly, a solution dosed with a mixture of linalool, geraniol, and citronellol scored less than two for tropical. However, when all four were blended, the tropical score jumped to a full four. (That may be what happens when brewers use Chinook because not only is it geraniol-rich, it also contains 4MMP.)

The Thiol Potency Indicator
The formula Nyséos proposes to measure thiol potency generates a TP indicator, but the lab also provides information about bound and free thiols. For instance, Calypso has a TP of 112, but 95 percent of that is bound 3MH potency and 5 percent bound 4MMP potency. To free bound thiols, Nyséos suggests using hops in the kettle. Citra, on the other hand, has a lower TP (57), but 33 percent is free 4MMP, 8 percent bound 4MMP, 1 percent free 3MH, and 58 percent bound 3MH, making it suitable for use in the kettle or dry hopping. Unfortunately, Citra doesn’t actually have a single TP. Its TP varies from one lot to the next.

For instance, Nyséos analyzed two different lots of Citra during its research. One contained two-thirds the amount of free 3MH as the other, but 50 percent more free 4MMP. During the aroma and flavor conference at Oregon State, Martin Steinhaus presented information from the German Research Center for Food Chemistry about 4MMP in forty-six varieties from five countries. Not surprisingly, the group concluded that variety was the largest factor in determining 4MMP concentrations. However, the research also found variations related to harvest year and provenance. The study did not take into account other factors—such as harvest maturity, post-harvest processing, and hops storage—that other researchers have reported may have a significant impact on the composition of essential oils, including thiols.

That’s why the possibility of a TP indicator number printed on a package of hops, along with a list of other components, is so appealing. It would measure the final product. For now, the cost of technology makes this look like a flying car, but Dagan is an optimist. “Thiol management is tricky in wine,” Dagan says. “But after twenty years, winemakers are able to produce great Savignon blanc wine with better management of thiols. So, I think that will be the same for beer in five years.”

FROM WHITE LABS:
Biotransformation

If you have been paying attention to the brewing world at all, you have heard the term “biotransformation''. Biotransformation refers to the interaction of yeast with hop compounds during fermentation. New research has emerged showing yeast to have the capacity to change various hop compounds into aromatic compounds that previously were not present, an approach that is becoming increasingly popular for juicy IPAs.

Yeast cells contain many types of enzymes that act as catalysts for a variety of biochemical reactions within the cell, often at varying activity levels. Some of these enzymes can trigger the conversion of bound hop compounds, resulting in unique aromas. Key enzymes identified in this biotransformation process include beta-glucosidase and beta-lyase.

Beta-glucosidase releases the aromatic terpenes from a non-aromatic glycoside precursor, such as geraniol from geranyl glycoside, while beta-lyase releases bound thiols (sulfur-based compounds) into free thiols (passionfruit and guava aromas). Beta-lyase activity in yeast has lately been the focus of brewing research because of the resulting contribution of tropical characteristics such as passionfruit and guava.

Bound Thiols
Free thiols, which are often responsible for contributing tropical aromas, are present in some of the most popular hops. However, many other hop varietals can contain higher amounts of odorless bound thiols. Yeast interactions from high B-lyase strains with these varieties of hops have been found to release these bound thiol compounds to free thiols resulting in new tropical aromas.

*The thiol concentrations in these less expensive hops can vary depending on growth conditions and season. The level of bound thiol present in the hops can directly be correlated with the levels of passionfruit and guava in a resulting beer.

IRC7
Beta-lyase enzymatic activity is strain dependent and can be traced back to the IRC7 gene. In collaboration with Oregon State University (Dr. Chris Curtin) and Virgil Gamache Farms, Inc., White Labs set out to screen for beta-lyase activity in our strains.

The results showed varying degrees of beta-lyase activity in the strains that were analyzed. With this information, we wanted to validate the theory that high enzymatic activity would directly correlate to free thiols and, thus, the tropical characteristics in a finished beer.

Activity Assay
We first started by extracting the enzyme out of the yeast cell to measure activity levels. They were compared with a known high activity control, Maxithiol, and known low activity control, S-288C. (As seen in FIGURE 1 BELOW). Strains with higher than 1 relative activity were considered high-activity yeast.

Brewing Trial
We brewed with some of these strains to test our theory and determine if the sensory attributes in a beer would be perceivable. Using Cascade, Simcoe, and Mosaic for the whirlpool and dry hop additions, we conducted a split-batch fermentation using our new high-activity B-lyase blend, WLP077 Tropicale Non-GMO Yeast Blend, and WLP001 California Ale Yeast, a strain that had shown low enzyme activity in the assay. After fermentation, we sent these beers to be analyzed by Gas Chromatography for free thiol concentrations and a blind beer sensory panel was conducted.

Levels of Free thiols such as 3-sulfanylhexan-1-ol Acetate (3SHA), aromas of grapefruit and passionfruit, were present and above the threshold in our WLP077 Tropicale Non GMO Yeast Blend.
(FIGURE 2 BELOW)

The last step was correlating the analysis results with actual flavor differences in the beers by conducting a sensory test.

From the side-by-side tasting comparison, we collected and summarized the following tasting notes:

WLP001 - Resin, Dank, Pine
WLP077 - Passionfruit, Peach, Vanilla

Based on the results of our description test, the WLP001 California Ale Yeast was perceived to be similar to a West Coast IPA with resin and dank notes coming from the Cascade hops. The WLP077 Tropicale Non GMO Yeast Blend was described as juicy, passionfruit, and vanilla, along with less lingering bitterness.

The results from our directional difference test (ASBC Sensory-6) showcased a positive significant difference for a stronger intensity of passionfruit/grapefruit.

MORE INFO FROM WHITE LABS

FROM OMEGA YEAST:

First off, what does “Thiolized” mean?
Thiols are highly impactful aromatic compounds that can evoke intense tropical, citrus character reminiscent of juicy passion fruit, pink guava, and freshly zested grapefruit peel. The term “Thiolized” refers to our engineered yeast strains that have the ability to biotransform the thiol precursors found in malt, hops, and grape-derived products into free thiols. Brewers can unleash these previously inaccessible tropical aromas into their beers simply by switching to a Thiolized yeast strain.

Select which Thiolized strains work best for you.
Tropical thiol aromas are a perfect addition to hazy IPAs, West Coast–style IPAs, and hoppy lagers. We have Thiolized yeast strains for each of these, but you can pick and choose how you want to add thiol aromas to any style.

Cosmic Punch (OYL-402)
We first introduced the Thiolized series in 2021 with Cosmic Punch, a Thiolized version of our British Ale V strain. Cosmic Punch is great for hazy beers with added nuances of grapefruit, passion fruit, and guava aromas. This is an excellent candidate for a hazy house strain, as its thiol output is versatile, complementing hop combinations without stealing the show.

Helio Gazer (OYL-405)
With enhanced Thiolized capabilities, Helio Gazer boosts thiol biotransformation 200 times above sensory threshold and 20 times more than Cosmic Punch. Even in the juiciest of IPAs, expect distinctive guava and New Zealand sauvignon blanc–like aromas, along with the beloved haziness of its parent strain, British Ale V. This is our most thiol-forward hazy strain.

Star Party (OYL-404)
Star Party packs a huge punch of thiol aroma while maintaining the clean, reliable fermentation behavior of its parent strain, the renowned Chico ale strain (our West Coast Ale I). If you are looking for a fresh take on old-school West Coast IPAs, this one’s for you.

Lunar Crush (OYL-403)
Lunar Crush is great for hop-forward lagers and is far from traditional. Expect crisp, snappy, and refreshing thiol aromas of grapefruit in conjunction with that lager drinkability. This strain offers a new approach to brewing lagers and the ability to bring thiol aromas to the forefront.

Some technical points when brewing with Thiolized yeast …

Thiol sensory:
We’ve found that when it comes to maximizing thiols, the simplest approach is often the most effective. From a sensory standpoint, thiols are bolder and much more obvious in a blonde ale or lager recipe than they are in an IPA. This is because IPA recipes already have an intense layering of hop aromas. Brewing an IPA with Thiolized yeast leads to an added overall tropical sensory perception, rather than an isolated passion-fruit aroma. An analogy would be adding passion fruit to fruit punch to make tropical fruit punch.

To emphasize that defined passion-fruit aroma, pare down your recipe to a simplified grain bill with a majority barley base malt (wheat and oats have little, if any, thiol precursors). Try mash-hopping with varieties such as Cascade, Saaz, Calypso, or Motueka. Adding hops so early in the brewing process may seem counterintuitive, but it turns out that using hops in the mash is an efficient way to add thiol precursors from hops and get even more tropical aromas from Thiolized yeast. To avoid overpowering thiols with intense hop aromas, pull back on hopping rates in the whirlpool and dry hop.

As you can see, when it comes to thiols, sometimes less is significantly more.

Efficiencies and sustainability:
When utilizing our Thiolized strains, you can reduce your hopping rates while still achieving big tropical flavors and aromas. Don’t forget that barley base malts carry the load when it comes to thiol precursors. Designing simpler, more efficient grain bills can maximize thiol output and yields. Perhaps most exciting: Playing around with new regional malts and hops supports local growers, but it also may provide rich sources of thiol precursors and thus a new perspective on terroir in beer.

How were these strains developed?
Traditional yeast strains are inefficient and mostly incapable of biotransforming thiol precursors in wort. Using CRISPR/Cas9, a genetic editing tool, we can enhance a yeast’s ability to unlock these thiols to their free, aroma-active state. With access to these thiol precursors, brewers can generate rich, tropical fruit–forward aromas in their beer in a way that hasn’t been available in the past.

In short, brewing beer just got a hell of a lot more interesting.

FROM OMEGA YEAST:

WHAT’S THE DEAL WITH MASH HOPPING?
Using hops so early in the brewing process at well below boiling temperatures may seem counterintuitive, but it turns out that using hops in the mash provides an opportunity to convert thiol precursors into a form that makes it possible for our Thiolized strains to generate rich, tropical aromas.

In developing Cosmic Punch, we included Cascade hops in the mash for a test batch and found that 3SH levels increased nearly tenfold with Cosmic Punch in comparison to its parent strain, British V. When comparing these 3SH levels to those found during traditional whirlpool hopping, Cosmic Punch still generated about twice the free 3SH when measured in nanograms per liter (ng/L).

In other words, mash hopping gives brewers the opportunity to extract additional flavor potential from hops, especially those not typically prized for their intense aromatics. In our brewing trials, we have found Saaz, Cascade, Calypso, and Motueka to be effective as mash hops, generating a particularly pleasing thiol output. Researchers have also found high precursor levels in Apollo, Eureka, Hallertau Hallertauer, Nugget, and Perle hops.

Unfortunately, we can’t yet say definitively which other varieties of hops will be best for mash hopping. Environmental factors like temperature, elevation, and precipitation, and even lot-to-lot variance can affect the composition of a given hop variety. In general, we recommend using lower alpha acid hops to avoid over-bittering the beer and to save your expensive aroma hops for later additions where they can really shine without being lost during the boil.

WAIT A SECOND… YOU CAN GET THIOLS FROM MALT?
One of the most interesting discoveries in all of our research into thiols has been the emerging information about thiol precursors in malt. In one of our trials, we brewed a test batch with 100% two-row malt and added no hops, letting our Thiolized yeast run with what was available, and the results were incredible — we observed an increase of free thiols nearly ten times sensory threshold!

Much like hops, we don’t yet know which types of malt have the highest levels of thiol precursors available, but from our benchtop trials, unkilned and lightly kilned malts have shown the greatest increase in thiol output over a control (non-Thiolized) strain.

This presents an exciting opportunity for brewers to work with local maltsters and begin to discover the potential of malt terroir. Barley is abundant in thiol precursors, but as with any agricultural crop, the exact makeup of barley will vary from region to region. We recommend trying out one of our Thiolized strains in a relatively simple recipe, like a blonde or pale ale with minimal hop rates to let the yeast really shine and experience first hand how these thiols are expressed in the finished product.

WHITE LABS 10th ANNIVERSARY ALE - SPLIT BATCH

USA EAST COAST HAZY IPA - ALL GRAIN

WHITE LABS BETTER HAZE AHEAD - SPLIT BATCH

USA EAST COAST HAZY IPA - ALL GRAIN

WHITE LABS BETTER HAZE AHEAD - SPLIT BATCH - MASH HOPPING

USA EAST COAST HAZY IPA - ALL GRAIN

WHITE LABS BETTER HAZE AHEAD -WITH PHANTASM

USA EAST COAST HAZY IPA - ALL GRAIN

PRIVACY POLICY | TERMS OF USE| SUBSCRIBE TO NEWSLETTER

© 2024 WILD ABOUT HOPS^® NZ
SAVE MONEY - BREW BETTER
NZ's #1 SUPPLIER OF HOP PLANTS FOR BREWERS

PHONE: 0210 2407203 | CONTACT