Conclusion of Experiments:
The "Sour Starter" created a highly objectionable nail-polish/solvent odor after ~4 days and was tossed.
The lacto starter with 2nd runnings smelled/tasted of lemon with a pleasant acidity after ~ 7 days, increasing in acidity up to ~ 14 days. However, I also detected some solventy character in this sample as well.
I am somewhat confused as how the solvent flavors were produced in the starters. The compound normally responsible is ethyl acetate, phenols, or longer-chain alcohols, all of which requiring ethanol fermentation to produce their respective reactants.
As close as the soured wort was to being a viable starter, I believe a few procedural tweaks will create a usable product:
- Controlling the starter temp at 100F
- Monitoring the pH (I do not have a pH meter) and using starter at optimal pH
- Significantly reducing O2 uptake (lots of head space in flask; took several samples) to ward off growth of acetobacter
Milling the grain myself may also help reduce unwanted flora on the grist. Currently, my LHBS mills my grain.