Brew Dudes

Homebrewing blog and resource

Culturing Bottle Dregs Follow Up

Two weeks ago I talked about culturing up some souring microbes from a bottle of Petrus’ Oud Bruin.  In that post I added a little bit of starter wort to the bottle sediment to see if I could get a culture going.  The plan was to give it 4-5 warm days in the bottle then step up to a 500mL culture in a larger flask.

Well…. I didn’t quite get around to it as soon as I should have and it seems to have failed.
I looked at it around day 5 and saw a distinct increase in the volume of the sediment in the base of the bottle.  Something had indeed begun to grow.  The wort also seemed to be a little ‘ropey’ suggesting an even more dynamic culture that I would have thought so soon.  I didn’t really get back to the culture until a full two weeks after “pitching”.

Now as you can see in the video, there is a good head of mold on the top of it and that ropiness is connected to it.  I suspect maybe even at day 5 those ropes were the start of mold.

Now I am left to wonder:

  1. Did the culture not take off at all.  Was the sediment just not viable?
  2. Did my starter wort (1.030 OG) not provide enough nutrients to get the microbes off the ground fast enough?  Hopefully a good culture would have lowered the pH to the point where the mold wasn’t going to grow.
  3. Did I contaminate the wort myself at the outset and the project failed because of that?
  4. What to do differently next time with a different sour cultured beer?

I am still thinking it over, and I won’t be deterred.
Do you have any advice for me on this one?
Leave us a comment and tell me what I did wrong!


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  1. Fred

    Hmm… I have never tried culturing in the original bottle. My technique is as follows:
    1) Leave at least 1/4 of the dreg intended bottle intact.
    2) Create 1L 1.040 starter in a well sanitized container.
    3) Cool your starter to 65-70F.
    4) Sanitize the neck of your bottle, agitate the bottle well and pour into your starter.
    5) Wait two days, and give it a sniff. If it smells bad, try something else.
    6) Wait at least a week, another sniff, if its smelling okay, repitch the entire thing into an additional 1L of wort.
    7) After another week, pitch this entire thing into 3.5-5Gal of some “test” beer you want to brew.
    8) Wash the yeast cake on that beer as your first generation harvest.

    This worked well for me for an Orval harvest. I am not sure what you’re gonna get out of a sour. I have an acquaintance that is a hard core sour brewer, and he is adamant about never harvesting from sours. He says start with a Wyeast/White labs and only harvest your own cake. I can bring this up to him to see what his opinions are though. Apparently most bottle dregs are simply lager yeast they use for carbonation only. This apparently varies greatly between breweries though.

  2. Jeff

    Next time try dropping the PH a bit on the wort with acid/acid malt? The dregs are going to be hurting, but I have to assume they’d be used to the lower PH, brett and lacto especially. That could help the dregs out-compete the nasties.

  3. Mike

    Interesting idea. I have some pure lactic acid I could use as well as pH strips to check the wort with.

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