Lacto Culture Experiment

Ingredients
1

This weekend I brewed a beer I intend on souring with lactobacillus. I wanted to try out a few simple ways to culture up lacto from the grist. I made two cultures with these methods:

  1. A “Sour Starter” from a recent issue of Zymurgy - basically a few teaspoons of grain in a pint of 1.030 sugar solution.

  2. A pint of second runnings, taken from the vorlauf - OG = 1.030.

To ward off beer-spoilers, I’m going to let the cultures work until the pH has dropped below 4.3 and the media has no off flavors/aromas. I’ll take the one that smells best for my beer.

To run the full experiment, I’ll draw off a bit of green beer from primary to fill both starter containers (growlers). I’ll chart acidity and flavor development (qualitatively). I intend on reporting my results back here.

Anyone else tried something similar?

2

sounds like a good experiment.

Ive always wanted to taste side by side results of different lacto methods.

The ones youve mentioned as well as doing a lacto starter at warm temperatures and getting it into the beer at full steam ahead.

3

I’ve had really good results with that method for Berliner Weisse.  Except I add a couple of handfulls of grain per 2 quarts, acidify the starter to 4.3 to start with, add the lacto to the starter, and keep at 100-120F for 3 days.  Then repeat with the wort for 3 days at 100-120F, then add the ale yeast.

4

I don’t have a pH meter at home, or else I would’ve adjusted with lactic acid.

Also - if these methods are successful, it will be a good way to cheaply produce lacto cultures on a commercial scale without any additional materials (besides a culturing vessel).

5

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.