Starter smells like butterscotch. Do I need to worry?

Discussion in 'Homebrewing' started by DVoors, Jul 9, 2015.

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  1. DVoors

    DVoors Zealot (627) Jan 6, 2014 Indiana

    So, I made a starter the night before last for the German Pilsner I will be brewing this afternoon. I made a 4.5 quart starter using 1 lb of X-Light DME, and pitched 2 vials of WLP830 (German Lager Yeast). I don't have a stirplate, so I just use the "shaker" approach. I have been fermenting the starter at room temperature (about 70 - 75 degrees). When I went to shake the starter last night, it smelled like straight butterscotch. While I know that Diacetyl is a common byproduct of fermentation and a precursor for a bunch of other compounds that can later reduce the levels of diacetyl to below our taste threshold, I know that it can also sometimes be caused by infection/sanitation issues. My question is do I need to worry about pitching a starter that is obviously loaded with diacetyl into my wort? Is this common for diacetyl to be produced in the starter and if so, will it go away or be diluted to levels below flavor threshold once it is pitched into the wort and fermented at proper lager temps, or would I be better off starting fresh with new vials? Thanks!
     
    #1 DVoors, Jul 9, 2015
  2. JackHorzempa

    JackHorzempa Grand Pooh-Bah (3,375) Dec 15, 2005 Pennsylvania
    Society Pooh-Bah

    Early in fermentation (and your starter has only been going for less than 24 hours) lots of diacetyl is produced. Below is a link to an article by Dr. Chris White on this topic.

    For a batch of beer the level of diacetyl is reduced later in fermentation: “Yeast reabsorb diacetyl and convert it to acetoin and subsequently to 2,3-butanediol.”

    If you decide to pitch your entire starter the ‘excess’ diacetyl will be reduced during the primary fermentation of your beer.

    Alternatively, you could decide to cold crash your starter and decant the starter beer contents.

    It is your choice how you want to proceed here. Cold crashing and decanting will take more time.

    Cheers!

    http://www.whitelabs.com/files/Diacetyl_Time_Line.pdf
     
    #2 JackHorzempa, Jul 9, 2015
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  3. DVoors

    DVoors Zealot (627) Jan 6, 2014 Indiana

    Thanks Jack!
     
    #3 DVoors, Jul 9, 2015
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