Jeff Young

Also, since the sequencing doesn't discriminate between dead cells and living cells, a type of control we put in to place was before anything was inoculated, we plated a portion of the nutrient-rich buffered starter (basically just LME, CaCO3, and yeast nutrient) after autoclaving to ensure nothing grew. All the samples came back negative (no growth). And yes, that would be good to note in our results :)

Thanks, updated. Except for QS. Here's a link for that: https://en.wikipedia.org/wiki/Quantum_satis

We'll also be looking at the organic acid profile produced in the wort. I expect the bulk of the acids to be the typical ones produced by LAB (mostly lactic, obviously), but I'll be interested to see what low level secondary acids are produced and how different grains might have different "signatures."

Thanks Indian Joe Brewing! We'll let you know when we start getting some results in!

Thanks Rick!

I posted this in the main comments section as to why at Blue Owl we do particularly timed wort-sourings----if we do everything right in the brewery and hit our target conditions properly, we can achieve our "maximum potential titratable acidity" for the wort generally in well less than 24 hours. As the density of the wort goes up, so does the buffering capacity, and thus so does the wort's ability to resist pH change and allow the souring agents to create acidity until the pH drops below about 3.3. After it drops below a pH of about 3.3, very little additional acidity is created. So as a brewery, we try to get the level of acidity (TA) in the least amount of time. The beer we are tested is a pretty typical gravity wort (around 12P) and we find it hits the level of acidity we desire (around 0.65% as lactic acid) in about 18 hours. So to be honest, the data points will all actually probably be under 24 hours and the last one will be taken when the TA is about 0.65%.

The really "important" data points will be a) the grain, b) the initial inoculated wort sample, and c) the final inoculated sour-wort sample. We will also be taking corresponding TAs, gravities, buffering capacity, and pH of the samples.

Hey Klara, if we do everything right in the brewery and hit our target conditions properly, we can achieve our "maximum potential titratable acidity" for the wort generally in well less than 24 hours. As the density of the wort goes up, so does the buffering capacity, and thus so does the wort's ability to resist pH change and allow the souring agents to create acidity until the pH drops below about 3.3. After it drops below a pH of about 3.3, very little additional acidity is created. So as a brewery, we try to get the level of acidity (TA) in the least amount of time. The beer we are tested is a pretty typical gravity wort (around 12P) and we find it hits the level of acidity we desire (around 0.65% as lactic acid) in about 18 hours. So to be honest, the data points will all actually probably be under 24 hours and the last one will be taken when the TA is about 0.65%.

For this particular experiment, we'll start with what we know works (CaraPils) and would like to also test the wort that we collect and save to inoculate the next batch to see how it changes over the course of a week. That's kind of our of scope for this project, but if funds come through, perhaps we can tack on a couple other tests like that. Perhaps start building a library of "the best" grains to make sour-worts with.

Hi Andrew. I think making starter cultures from Weyer. acid malt is a good idea. I've used many different malts and seen many different results. We inoculate the entire batch of wort with the culture from the grain during the brew day OR we will pitch a bit of the previous beer's sour wort. So we can, and do want to assess "starter cultures" from our particular grain. We use Briess' Carapils as our inoculant. I've also used Weyer Cara Foam and even a few C-10s from different maltsters. We find the best results from the lowest kilned malts. A big factor for us is that we inoculate post-mash with additional malted grain. So the malt has to be basically "crystallized" or the wort will throw one terrible starch-haze! That's why CaraPils has been our grain of choice...although we're looking for alternatives, just haven't seen one that fits our criteria as well.

Hey Matthew, I'm going to write up a more detailed description of our souring process under lab notes, but for right now I can tell you that we do indeed purge our incubation tank (40bbl modified kettle) with CO2 and we hold every batch at 113F +/- 2F