Brewing Master » Brewing Beer » O captain, mercaptan!
O captain, mercaptan!
Question:
As a former American, now for many long years resident in Australia, I get nostalgic for odd things about home.. Such as, believe it or not, the smell of skunk on the Summertime evening breeze. (They don’t have that animal, or any of its close cousins, here.) So I’ve tried to remind myself of the smell by sitting some homebrew out in transparent Corona bottles, in the noonday sun. But no dice. It turns out a bit strange, granted, but no relation to skunks. Can someone help me get the real skunk smell? What do I have to do?
Buy some or have a chemist friend buy some for you. Butyl mercaptan (also called butane thiol, if memory serves) is readily available. Just be careful to note the boiling point before opening. Now you must endure a story. A rather lovable biology teacher in my old high school runs an annual experiment in selective excretion on his classes. He feeds us hapless victims some asparagus (canned in our case… yetch) and asks us to note the smell of our urine over the next twelve hours or so. Have you ever tried to remain inconspicuous while sticking you head into a urinal? Anyway, the glorious odor wafting forth from our pee was reportedly methyl mercaptan. Our teacher was a curious sort and wanted to know what the pure chemical smelled like. On the day the bottles arrived he hurriedly followed the instructions. "Place bottle in a bucket, place bucket in fume hood, and turn on fume hood before removing stopper." He failed to note that said bucket should be filled with ice water because the boiling point of methyl mercaptan is well below room temperature. When he knocked the glass stopper off, the entire pint boiled away, up the fume hood, and onto the roof. Where, since this gas is heavier than air, it proceeded across the roof, down the sides of the building, and back into the open windows. The smell was incredible, but nothing like our human processed asparagus. We did get a two day break from science classes, though. — david wiley "It’s no exaggeration to say the undecideds Intergraph Corporation could go one way or another." 205-730-6390 – George Herbert Walker Bush
Response:
Isomerized hops are supposed to be resistant to the effects of light causing the skunkiness (Miller is infamous for doing this to allow shipment of beer in clear bottles). Since boiling hops partially isomerizes them, you might be able to get a skunky/catty [1] aroma if you don’t boil them. Try making a hop tea and adding that to the cooled wort (though this may result in an infection).
No, it’s the other way around: isomerized hops alpha acids are the substrate for the skunking reaction; fresh hops, that have been growing in the sun for weeks are not skunked. You probably were thinking of _hydrogenated_ iso-alpha acids. The reduction of a double bond prevents the initial step of the light-induced reaction (a Norrish type II cleavage, for the initiates). Pierre — Pierre Jelenc
Response:
I checked my library of beer information (now that I’m at home) and found a reference to a Fall 1991 article in the American Society of Brewing Chemists titled "Sunstruck Flavor in Beer". This article noted that beers with a higher level of adjuncts had a higher level of skunkiness (from the 3-methyl-2-butene- 1-thiol molecule) than beers whose variability was in the color of their bottles. The authors concluded that riboflavin (vitamin B-2) is one of the important factors causing formation of light-struck aroma. So, if you want skunkiness, try adding a little B-2 to your beer. Bob Devine
Response:
Adding skunkiness on purpose is harder than seems true. When I worked for DEC, one the homebrewers tried to add it by hanging a circular fluorescent light around the carboy’s neck. He also tried setting it out in the sun. Isomerized hops are supposed to be resistant to the effects of light causing the skunkiness (Miller is infamous for doing this to allow shipment of beer in clear bottles). Since boiling hops partially isomerizes them, you might be able to get a skunky/catty [1] aroma if you don’t boil them. Try making a hop tea and adding that to the cooled wort (though this may result in an infection). Bob Devine [1] British brewers call the distinctive sulfur-based smell "catty" because the UK does not have any skunks in the region; the French skunk, Pepe LePew, doesn’t count. 
Response:
As a former American, now for many long years resident in Australia, I get nostalgic for odd things about home.. Such as, believe it or not, the smell of skunk on the Summertime evening breeze. (They don’t have that animal, or any of its close cousins, here.) So I’ve tried to remind myself of the smell by sitting some homebrew out in transparent Corona bottles, in the noonday sun. But no dice. It turns out a bit strange, granted, but no relation to skunks. Can someone help me get the real skunk smell? What do I have to do? [P.S., I know this sounds tongue-in-cheek, but it actually isn't.] Thanks Sydney, Australia