Thiolize This! (Fruited Sour)

I’ve been having fun playing around with some of the new hybrid yeasts from Escarpment Labs. A while ago I posted about using their Hydra yeast in an IPA that combined 4 decades of brewing trends into one beer. This post is about another using another of Escarpment Lab’s hybrid yeasts – Thio Libre. Thio libre has a high lyase (thiol-releasing) activity. Normally, brewers use this to release tropical flavours from classical American hops (e.g. Cascade). This produces a beer with mango and other tropical characters, but without the need to buy pricey modern hops. This is achieved by liberating fruity-tasting thiol groups from cysteines (proteins) in hops and malt. But, being me, I didn’t do that. Instead, I instead decided to look at what would happen if I thiolized fruits. Thiolize This! is based on my peach and mango kettle sour recipe, but swaps out the usual US-05 for Thio Libre.

My rational for doing this is, like hops, fruits get some of their flavour and aroma from thiols. And like hops, fruits have bound (e.g. not flavour active) thiols. In theory, these can be released by a thiolizing yeast like thio libre. And, as with hops, there is the possibility of transforming the flavour of the fruit by releasing these thiols.

So how well did it work?

Thiolize This! – Recipe

Stats:

• OG: 1.050
• FG: 1.010
• ABV: 5.3%
• IBU: 8.5
• SRM: 3.7

Ingredients

Brewing

1. Mash-in at 64C for 90 minutes to create a highly fermentable wort. Warm to 75C to pasteurize, then cool to 40C.
2. Place ~1 cup of uncrushed pilsner malt into a boiled (sanitized) hop bag and place into the wort. Hold at 37C until desired sourness is reached (pH of ~3.5, 24-36 hours).
3. Remove bag of malt and bring to a boil; add hops and boil for 1 hour.
4. Add the coriander seed during the last 5 minutes of the boil.
5. Chill to pitching temperature, add fruit, and pitch yeast.
6. Ferment for 14 days, then keg and force carbonate.

Tasting Notes – Thiolize This!

Appearance: When young this beer was highly cloudy due to the unsetteled pectin from the fruit. In hind sight, I probably should have added some pectinase to the batch. Over time this cleared out, leaving a golden-coloured beer with a faint haze. While the head pours thick and rocky, it only lasts a few minutes – pretty typical for a kettle sour.

Aroma: The aroma is quite strongly that of peach, with a fairly noticeable mango note. However, it also has an faint but unusual aroma that reminds me of those soaps that grandmothers in the 1980’s used to love – sort of a fake “generic” floral scent…which was something I didn’t expect.

Flavour: Here, things start to go off the rails a bit. As you’d expect, the beer is modestly tart, with a dominant flavour of peach and mango. This yeast is not a highly attenuation strain. Despite my best efforts – e.g. using a low & slow mash – if finished overly sweet. Its not candy-sweet, but it is not the bone-dry, sharp and crisp beer that I know and love.

But where this beer really goes wrong is in what I assume are the thiols released by the yeast. That “grandmothers soap” aroma is even more apparent in the taste. It comes across as a floral flavour that fights with the fruit notes for dominance. It’s hard to put my finger on exactly what that floral note tastes like. It is close to the flavour of rose water, but also has hints of the flavour of culinary lavender. I’ll admit to not being a fan of either of those, but I think even people who like these flavours would find them out-of-place in this beer.

Mouthfeel: The beer comes across as medium-bodied. It is not as dry and crisp as I would normally expect for this recipe. After taste is a lingering peach and rose note.

Overall: This was an interesting experiment, but not one I’m going to repeat. I guess not all thiols are good thiols.

But, I am re-brewing the Four Decades of IPA Trends with the Tiol Libre yeast. So watch out for that post in a couple of months!