Skunked starter?

[luckybeagle]

I have a starter made from slurry whirling around on my stirplate. That stirplate was in my office window and exposed to sunlight. As a result, it is giving off a light "skunked" aroma, like a lightstruck beer.

I'm in Oregon--we're not used to sunshine, and we have some today for the first time in what feels like 6 months.

Wondering if decanting and pitching this starter will bring over a significant skunked aroma/flavor into the future beer (belgian golden strong, wy1388)? Or will dilution of it into 6 gallons of wort + fermenting this new batch take care of it/make it not perceptible?

 

[bruce_the_loon]

I take it the slurry was saved from a beer fermentation and reused? Skunking is caused by the UV light triggering a reaction with the isohumulones from the hops. If no hop organics were present in the slurry, then the skunked smell might indicate some other off-reaction or even spoilage.

A couple of papers on the topic refer to 3-methyl-2-butene-1-thiol as one of the most powerful flavour substances known with a threshold of 4 nanograms per liter for detection. The risk is probably not worth it in my mind.

 

[luckybeagle]

I take it the slurry was saved from a beer fermentation and reused? Skunking is caused by the UV light triggering a reaction with the isohumulones from the hops. If no hop organics were present in the slurry, then the skunked smell might indicate some other off-reaction or even spoilage.

A couple of papers on the topic refer to 3-methyl-2-butene-1-thiol as one of the most powerful flavour substances known with a threshold of 4 nanograms per liter for detection. The risk is probably not worth it in my mind.

Thanks! Since the 6 oz of slurry I used in the starter was unwashed and definitely has lots of trub and hop material in it, I'm sure it's due to light exposure. The erlenmeyer was right in the window getting full sun. I don't think I'm dealing with spoilage or infection, but I do have additional slurry that I could make a second starter from. That slurry is still in the fridge and has no skunk smell. Just hate wasting DME if it's a non-issue.

Assuming it's not an infection and just a 1.6L starter that is skunked--and will be decanted off--does that change your opinion? It's a very light smell, but if a few ounces of decanted slurry has the power to make 6 gallons of beer taste skunked, I'll scrap it.

 

[bruce_the_loon]

I can't be certain about the effect.

What you could try is to decant the liquid and rinse the yeast slurry once or twice with boiled and cooled water, then check whether you are still getting the smell.

 

[luckybeagle]

I can't be certain about the effect.

What you could try is to decant the liquid and rinse the yeast slurry once or twice with boiled and cooled water, then check whether you are still getting the smell.

I like that plan. I'll do that and report back. Thank you!