Common Beer Off Flavours – Garbage, Gas and yes Fart.
Off Flavour: Mercaptan
Chemical Name: Ethanethiol
What to look for: Trust me when I say you will know when you get it. Think drain, rotting garbage, sulphury or even the aroma of a fresh fart. This is the compound they add to natural gas to give it an aroma.
When does it occur: Can be caused during fermentation by particular yeast strains that are under stress. Also caused by yeast autolysis (basically a yeast cell that has died, ruptures and then releases several off flavours in your beer)
Will it disappear over time? Unlikely and likely that smell will increase substantially. Serve a beer with substantial levels of mercaptan and you may need to find some new friends.
Tips on how to reduce Mercaptan (ethanethiol)
Use the right yeast for the beer style
Good sanitisation practices
Rack your beer off the yeast cake within 4 weeks of fermentation start
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