Which factors influence thiol release?New OSU thiol research published

Understanding how to deliver key sensory compounds during biotransformation is central to making better beers. We are continually identifying topics and potential research partners, which is driven by our ethos to provide useful, scientifically rigorous resources for brewers using our products. In recent years, we partnered with Tom Shellhammer’s lab at Oregon State University (OSU), to explore thiol release and how brewers can use this mechanism effectively in their brewing process.

We are happy to announce the latest portion of this research is now published in the Journal of the American Society of Brewing Chemists, titled “Interactions Between Fermentation Temperature and Yeast Strain: Impacts on Polyfunctional Thiol Release and Beer Aroma.” This study builds on previous research and extends a practical step further by examining how temperature and yeast strain genetics influence thiol release.

For this study, five LalBrew® Premium strains were evaluated:  

OSU tested these strains at three different fermentation temperatures in an all-malt wort with the following thiols assessed:

The study’s goal was simple and framed around these two main questions:

We chose these questions to provide brewers effective levers to modulate thiol release. Below is a summary of the study’s key findings that brewers can utilize with additional resources found in the Lallemand BrewEd Biotransformation Resource Center.

Finding 1: Fermentation temperature has a big impact on thiol release

Temperature is therefore one of the primary drivers of free thiol levels, particularly 3SH. Both 3SH and 4MSP make notable contributions to the fruity character in beer, with these concentrations increasing above the sensory threshold at warmer temperatures.

We hypothesized that the lower 3S4MP levels were perhaps due to the hop varietal chosen for this study — Cascade, known to have lower amounts of this thiol precursor. Brewers should select either Mosaic® or Nelson Sauvin™ to promote 3S4MP levels.

Finally, we observed that thiols can be temperature sensitive, with both 4MSP and 3S4MP declining at 30⁰C.

Finding 2: Yeast strain selection is key for thiol expression

These differences most likely reflect variability in β-lyase activity (IRC7/STR3 gene expression). One possible reason for the high 3SH seen in LalBrew Diamond™ could be due to its’ historical genetic lineage. S. pastorianus is a natural hybrid of S. cerevisiae × S. eubayanus with S. eubayanus related to S. uvarum — a species known for elevated β-lyase activity and thiol release.

Analytical analysis is only one part of the sensory equation. Yeast strain characteristics also play a massive overall impact on the sensory profile of the beer overall.

Finding 3: Higher analytical thiol levels do not necessarily equal fruity/tropical aromatics

As with everything in brewing, there is always a balance to strike. Fermenting warm might produce more thiols, esters, and tropical aroma. However, undesirable effects can still happen if the temperature is not optimal for the particular yeast strain.

For lager strains, fermenting warm will risk the rise of sulfur off-flavors, which will detract from any lovely fruity aromatics the thiols produce. Equally, some tasters observed buttery flavors in ale strains fermented at low temperatures. This is most likely due to slow fermentation times of these strains.

It is not surprising that ale strains were rated as being highly fruity. Thiols alone do not tell a complete fruity flavor picture, they interact synergistically with esters, terpenes, and other aromatic compounds produce a holistic fruity/tropical profile in the beer. This confirms that aroma synergy, not thiol concentration alone, provides an elevated tropical character.

Practical takeaways

Overall, brewers should consider biotransformation potential in a holistic fashion where yeast selection, characteristics (including sulfur production), temperature sensitivity, and hop selection work together.