Mapping the sour beer microbiome

Methods

Summary

Mash-in/Lauter

Malted barley and water are combined in the mash tun to perform a typical single-step infusion mash.  A recirculation is performed on the resulting wort and then the wort is slowly run off into the sour tun.  The mash bed is rinsed with warm water as the runoff continues until we collect to total volume of the wort needed in the sour tun (36.6 barrels usually at about 12P gravity)

Wort Preparation for Inoculation

The total volume of wort is brought up to 165-168F to pasteurize.  The wort is then cooled to 113F +/- 2F.  The wort is cooled by recirculating through a heat exchanger and CO2 is injected into the wort and used to purge the air from the headspace in the sour tun.  

Inoculation of Wort

The wort at 113F is pumped through a small tank/chamber that we affectionately call "The MIU" (pronounced "mew" and stands for Modular Inoculation Unit).  I designed and had the MIU build to be a sort of small, controlled mash tun that holds the grains that are to be the vector for inoculation without clogging or channeling.  The wort flows over 50 lbs of Briess CaraPils and then is returned into the sour tun and mixed.  The wort is pumped through the MIU for 90 minutes (we have found that anywhere between 60 minutes and 4 hours doesn't have much effect on the outcome).  After 90 minutes, we chase the wort through the MIU with 180F water to purge and collect the last bit of wort.  We then seal up the sour tun, purge the headspace again with CO2, and mildly whirlpool the wort with the steam jacket temperature control set to 113F.

Incubation of Wort

The wort is tested periodically during incubation for titratable acidity and pH.  Once the TA reaches the desired level, we unseal the sour tun and start raising the temperature to boiling to cease further activity.