Understanding Thiols, what they are, and how they're a useful tool tool in brewing is becoming big news in the brewing industry. Do you want to know why? First lets get a very basic understanding of what Thiols are.
Thiols or thiol derivatives are organosulfurs known as the sulfhydryl (SH) or the mercapto group, that are often found bonded to a hydrocarbon group in organic chemistry like with alcohol in our fermentations. These compounds are found in a variety of areas in nature and are often used as additives or scent enhancers for odorless gases such as natural gas or propane. Even Skunks produce Thiols that aid them in their effectiveness as it pertains to self-defense, in the form of skunk spray, it contains 3 different Thiols. Since thiols are sulphur based in makeup, they tend to have somewhat offensive scents in concentration that most wouldn’t want in a beer. Lucky for us the levels and types we produce while brewing, especially with certain hop varieties, all those foul odors are generally below the threshold of where they're of concern in the overall balance of a beer. But that doesn’t mean we can’t capitalize on this organic compound using yeast specifically engineered to biotransform Thiols into pleasing, even desirable aroma profiles. It doesn't mean we can't use hop varieties high in bio-transformable Thiol goodies to enhance our beer now does it?
I’m not going to go into the science behind the chemistry and microbiology surrounding the interaction of Thiol conversion, if you’re interested in that there are other sources for information that I can’t even begin to compete with within my knowledge base. So you’re better off going to the source of the science for hardcore scientific information. I’d suggest Escarpment Laboratories from Guelph Ontario Canada for the detailed science behind Thiol Conversion from a microbiological level. But the general idea is that during yeast bio transformation with high IRC7 activity yeast an enzyme releases bound thiols within hop oils (terpenes) that once released produce fruity aromas that add to the nose of a beer. I’m no expert, by any stretch, but it’s my understanding that some hops are better suited to this purpose than others due to the overall makeup of their essential oils, although I have doubt there isn’t at least some transformation in a great percentage of hops. The amount of that transformation is based on the percentage of convertible and free terpinoids.
But I’m a homebrewer, a guy who makes mistakes and isn’t always perfect, and within those boundaries, I like to challenge the norm and see what I can accomplish with any new methodology and science available to me. Yeast that transforms Thiols into aromas like Papaya, guava sounds good to me, I can dig that. So what's my goal in this experiment? Ultimately it's to see how the average home brewer takes the same two beers, brewed the same, fermented at the same temperatures but with different yeasts, to see if any drastic differences occurred not only from a fermentation standpoint but also from an overall flavour and visual standpoint as well. Beer one will have Cali Yeast as it's fermenter and the second will be fermented with Thiol Libre from Escarpment labs. My goal is to see if the same two worts, with the same hop additions, will taste and smell drastically different from one another. So I brewed two beers, came up with near identical numbers pre-fermentation, added the same amount of yeast to each beer, just different yeast and let it ride. I added two dryhop additions and the differences coming out of the airlock right away were pretty noticeable. The Thiol Libre beer was much more Peach and tropical fruit, whereas the Cali yeast beer was straight citrus. My gravity samples were even more suprising to me, the two beers had drastically different colours. The Cali beer was were I intended it to be, a light copper/brown. The Thiol Libre sample on the other hand was much darker and amber in colour. Aroma on the samples were drastically different, the Cali yeast fermented sample smelled like your trypical IPA, fresh citrus, some dankness and a little resin on the end. The Thiol Libre sample on the other hand was much softer, had no dankness and the citrus was replaced with light stone fruits and mango. I did not sample the gravity samples, as I want to try these beers when the community does. Community feedback in part 2.