cabrillo II, blanc updates; diacetyl observations

a little while back I decided it was time to rack cabrillo II onto cherries and oak.

  • primary fermentation had been chugging along for close to four months, and since my first batch‘s ten months on fruit and wood imparted plenty of cherry and vanilla notes, I figured it was time to act.
  • this time around I went with around 116oz of tart cherries (likely closer to 100oz after separating the juice/water) and 1.5 oz of toasted french oak.  the initial batch of cabrillo’s 2.5 oz of oak initially dominated the beer with intense vanilla and took a few months to tone down, so I’m hoping the lower amount and shorter exposure complements the final product while allowing the cherries to shine a little more.

after racking cabrillo II, I decided to rack blanc onto the lees, oak, and remaining cherry pomace in cabrillo II’s primary fermenter.

  • I figured the bugs from cabrillo had already proven themselves as reliable and could only add more complexity to blanc.  since blanc was fermented in three separate containers, I also had a feeling that the three portions would need to be blended together in order to achieve a more consistent final product.  to test this theory, I compared samples from each fermenter during racking:
    • blanc A (3 gallon better bottle):
      • visible pellicle during fermentation
      • funky, sour aroma
      • aggressively sour body and finish
      • FG: 6 brix
    • blanc B (sealed corny keg under slight CO2 pressure):
      • no pellicle visible upon opening
      • burst of bretty diaper upon opening keg
      • strong brett/funky nose with hint of fruit
      • more fruity sourness with a dry, bretty finish (not as acidic as A)
      • FG: 7 brix
    • blanc C (sealed corny keg under slight CO2 pressure):
      • fruity brett aroma
      • acidic, fruity sourness
      • clean, bretty finish
      • FG: 7 brix
  • based on my observations, it seems that the additional oxygen allowed in by the better bottle increased both attenuation as well as perceptible sourness in the beer.  I should note that both the aroma and the taste of the better bottle-fermented portion seemed similar to my sanke keg-fermented sours (each of which had significant headspace in the keg).  since brett is anerobic, it seems that it thrived in the pressurized CO2 environment provided by the sealed corny kegs.

as a side note, after perusing some articles on homebrewtalk and the BBB I have come to the realization that the initial buttered-popcorn-jellybean flavor that initially dominated cabrillo I in the bottle was likely diacetyl produced by pediococcus, accentuated with vanilla imparted by the oak.

  • after checking my notes, it seems I didn’t notice any buttery flavors out of the fermenter, but after a few weeks in the bottle the flavor was dominant.  it seems that the pedio kicked out a lot of diacetyl upon bottling (maybe due to oxygen exposure during the bottling process?) and that the brettanomyces still in suspension cleaned up most of the diacetyl while in the bottle (I still can taste a fleeting note of sweet butter every now and again while pouring cabrillo I on draft, but it is hard to find in the bottles).
  • the lesson here? if the diacetyl was noticeable in the fermenter I would have likely waited it out while the brett cleaned up, but it is nice to know that the brett can still perform cleanup in the bottle/keg if need be.


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