Homebrew Experiment: Thiol Libre vs. Base Malts & Hops

Release the Thiols

Note, May 2023 - Thiol Libre has been updated to eliminate the risk of phenol production, which makes it easier to experiment with base malts. For the most up-to-date guidance on using Thiol Libre, see its Tech Sheet

I’m a homebrewer. As a homebrewer, I get to experiment. The pros have to worry about producing a beer that their customers will love (or at least like). Not us homebrewers. We are the mad scientist types; conducting awesome beer experiments in our basement or garage and enjoying the fruits of our labour. We can experiment with new yeasts, ingredients, and processes and see just how it affects our finished product. In this blog post, we are going to do just that; take the same recipe and tweak ingredients slightly to see how the results differ.

For all the batches in this experiment, we will be using Escarpment Lab’s Thiol Libre yeast. This unique yeast creates tropical flavour and aroma without using your big money hops like Citra and Mosaic. These expensive hops have lots of free thiol compounds which contribute to the wonderful aromas like Sauvignon Blanc grapes, guava, grapefruit and passionfruit. 

Many of your aromatic hops have large amounts of free thiols which is what makes them so popular for big tropical hazy IPAs. However, less expensive hops like Cascade or Saaz have lots of thiols too, they are just trapped within the hop, waiting to be freed. That’s where Thiol Libre comes in. The yeast has an enhanced IRC7 enzyme which helps release those bound thiol precursors and help create a wonderful tropical aroma.

However, it remains a bit unknown how Thiol Libre interacts with different base malts. Escarpment reported some differences and potential issues, such as certain Pilsner malts from the 2021 crop year producing unexpectedly high phenolics when using Thiol Libre. 

Escarpment labs has some awesome resources that dig into the science and best practices for using Thiol Libre and they can be found here: 


To evaluate the effect that specific ingredients have on the fermentation of Thiol Libre yeast. 

To conduct this experiment, we are going to take the exact same recipe, brewed three different times. Each time, we are going to change a single ingredient slightly. For the first comparison, we are going to use the same recipe and change the brand of the base grain. For the second experiment, we are going to keep everything constant except use fresh wet hops instead of dry pellet hops. Since Thiol Libre is a relatively new strain, I’m going to boldly claim to be the first person to ever brew with wet hops using this yeast (I have no idea if this is true).


Brew Day(s)

For this experiment, I needed to brew three batches of beer. For the recipes, I went with a nice, hazy single malt pale ale. My goal was to make a recipe that would be great for summer days; nice and tropical with a restrained ABV. 

Recipe:  Thiol Libre

Batch Size - 21L

Original Gravity: 1.056

Final Gravity: 1.015

ABV: 5.4%

IBU: 25

Colour: 3.5 SRM


  • 100% 2 row malt

Mash Profile:

  • 67°C for 60 minutes

Hop Additions:

  • 2 oz. of Cascade (6.6% AA) in the mash
  • 1 oz. of Cascade (6.6% AA) at 5 minutes remaining the boil
  • 2 oz. of Cascade (6.6% AA) in a whirlpool for 20 minutes at 80°C
  • 2 oz. of Citra (12.3% AA) for a dry hop at the end of fermentation


  • Escarpment Labs Thiol Libre


  • 18°C for 10 days

Brewfather link to the full recipe including water profile: https://share.brewfather.app/vzhqq82BMut92C

For the type of hop, I needed a variety of hop with lots of bound thiols. Thiol Libre would unlock these compounds and boost tropical flavours in the finished beer. Certain hops have lots of bound thiol precursors like Cascade, Perle and Saaz. The fact that a friend was growing some Cascade hops in their backyard made my choice really easy. I would use Cascade all throughout the hot side and then a single dry hop of Citra at the end to really max out the tropical aromatics.

In order to boost the release of bound thiols, I used a technique called mash hopping. This is when you add hops directly to the mash. These hops were added on top of the grain and left in the mash for the entire time. Since the temperatures during mashing are kept low, no isomerization occurs and no hop bitterness is imparted into the beer. What is imparted by mash hopping is more thiol precursors in which the Thiol Libre can feast upon during fermentation.

For a detailed look into why we can mash hop, check out Scott Janish’s blog post here.

The first batch that was brewed was the control for this experiment. It featured 100% Rahr 2-row malt and used cascade pellets.

The second batch would switch the base grain to 100% organic 2-row from Ontario maltsters Against the Grain. Bound thiol compounds don’t just come from the cascade hops but the malt as well. The question that the experiment is trying to answer is if by switching the brand of 2-row in the mash, would different amounts of released thiol precursors have an effect on the finished beer. This batch would use the same cascade pellets as batch #1.

The final batch to be brewed would use the same Rahr 2-row as the original batch. This time, we would be swapping out the pelletized cascade hops with fresh wet cascade hops right off the bine. Wet hops are freshly picked hops that haven’t been dried yet. These are the freshest hops you can get but only available around harvest time in late August and early September. Since these hops are fresh, their moisture content is quite high. Therefore, brewers need to use a larger weight of these hops relative to their dried and pelletized counterparts. For this experiment, I used 5 oz of wet hops for every 1 oz of dry hop that the experiment called for. A friend of mine kindly donated all of the wet hops for this experiment from his backyard hop collection. The question that this batch seeks to answer is if the fresh Wet hops may contain more bound thiol precursors relative to pelletized counterparts. 


Both batches were placed into separate fermentation chambers and left to ferment at 18°C. Thiol Libre has a temperature range of 17°C-23°C but Escarpment Labs recommends the lower end of that temperature range for the best aroma. 

At the end of the 10 day fermentation, I took my gravity measurement and proceeded to cold crash. This is also the time when I dry hopped with 2 oz. of Citra to really boost the tropical flavour. Although many brewers dry hop their beers at fermentation temperature for 3, 5 or even 10 days, I’ve been dry hopping during my cold crash with excellent results. It’s a quick, cold dry hop with minimum contact time and maximum hop extraction. 

Scott Janish backs up the science of a quick and cool dry hop in this blog post.

Taste Test

The true test of this experiment would be to see if the slight tweak in ingredients actually made a difference to the finished product. I conducted a variety of blind taste tests to anyone who would sample my latest beers. Their palates ranged from casual beer drinkers to BJCP certified judges. Each person was given a total of six samples over the course of three rounds. Each round would be broken into three samples of beer; two from one batch and one from another. The test would be to see if they could differentiate the unique brew. 

Out of a total of 24 participants, 21 were able to distinguish the Rahr vs. Against the Grain two row malt. When testing the pellet hops vs. wet hops, 19 out of 24 participants were able to identify the outlying beer. Finally, 21 out of 24 participants were able to tell the wet hopped beer with Rahr from the Against the Grain beer. The results were overwhelming. The beers could easily be distinguished from one another.

I was able to get some great tasting notes from the staff at Escarpment Labs as well. The staff all had sensory training and could easily distinguish the three beers. They found the Rahr base malt version to have moderate fruity/thiol aroma with low/indistinguishable phenolic aroma of clove or spice. The wet hopped beer had a much higher fruity characteristics but was slightly more phenolic. The final beer, with Against the Grain malt, had the low amount of fruity aroma and the highest phenolic aroma. This third beer also had some slight plastic or medicinal characteristics. Overall, the feedback from Escarpment Labs was that each of the beers were clearly different and the wet hopped beer was most enjoyable.

From my own taste testing, I found that all three beers were noticeably different. Each beer was unique and delicious in its own right. The control batch with Rahr 2-row malt had a full malt flavour with great grapefruit aroma and flavour. The wet hopped beer was unique in its own right. The wet hops brought out tropical flavour and the aroma was a unique mix of tropical citrus and pleasant lilac aroma. I found the Against the Grain batch was lacking in malt character as well as hop flavour and aroma. However, the tropical notes were definitely present as well. There was much more grape and passion fruit characteristic than a typical cascade hopped beer. Overall, all three beers could easily be distinguished which correlates to a different level of unbound thiols in each of the control ingredients.


Brewing three of the same beer with new, unique ingredients was an awesome experiment for a homebrewer. It allowed me to dial-in the procedure and really focus on each of the ingredients. It also allowed me to explore new, unique processes such as mash hopping and wet hopping. I’m a strong supporter of changing things up and trying something new no matter what level of brewing experience you have.

I was pleasantly shocked with the tasting results on these beers. Tweaking the ingredients slightly led to three unique beers that were easily distinguished by all tasters, regardless of experience. In the end, I am able to enjoy three beers that are similar on paper but with a very different finished product.

Overall, this experiment was a success. Three very distinct beers were created using very similar ingredients. The experiment achieved its goal; each ingredient has its own amount of bound thiols and tweaking those ingredients have a definitive effect on the finished product.

This experiment also opens a whole new series of possible tests with this yeast. Each tweak of the ingredients produced unique flavour and aroma combinations that could create many distinct beers. 


About the Author:

Tyler Ustrzycki, a husband, father, homebrewer and engineer from Waterdown, Ontario. You can find Tyler on IG @grindstonebrew.


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