Cedar Rapids Brewing Society

I've been doing some reading on how Lactic Acid is produced by Lactic Acid Bacteria (LAB).

The link I found at http://textbookofbacteriology.net/lactics_2.html shows that homofermentative LAB including lactococci and pediococci catabolize one mole of glucose (dextrose/corn sugar) into two moles of pyruvate. From there the pyruvate is reduced to Lactic Acid.

Greater than 50% of the available glucose is converted to Lactic Acid.

http://www.brewmorebeer.com/brewing-sugars/ shows typical wort composition at approx 8% Glucose.

This leads me to believe that increasing the percentage of glucose (corn sugar) in the wort would lead to an increased amount of lactic acid. At least down to the tolerance level of the bacteria, which is about PH of 4 or below.

I read many complaints about sour beer not getting sour enough and have to believe if the issue is that the the available glucose to the LAB is getting noshed on by the Saccharomyces before the LAB can get to it.

If glucose is metabolized by the LAB first, then the trick appears to be, instead of taking gravity readings, take PH readings and then boil to kill off the bacteria when the PH hits where you want it. Just like a Berliner Weiss soured in the kettle.

I expect that the total sourness can be increased quickly by feeding the LAB an increased amount of glucose first, then pitching yeast or a mixed culture with additional glucose after the target PH is reached to get a "normal" fermentation.

This should work for all sour beer types. Granted there are other benefits to the traditional long term aging and the hyperattentuation from mixed culture fermentation etc. and the results may end up rather less complex.

Basically the idea is:

1. Add additional glucose and LAB to wort
2. Achieve Sour-er Beer
3. Profit

Or just add liquid Lactic Acid if you want to cheat.

Any feedback is welcome. I just needed to get this out of my head.



Cedar Rapids Beer Nuts Secretary

"Payday came and with it beer"
- Rudyard Kipling

Interesting.  I always assumed the LAB had to eat a fair amount of the sugars before you let the sacch get at it in order to make a sour beer.  I've never considered that the LAB won't make much lactic acid unless they're fermenting glucose.

This strikes me as a straight-forward hypothesis to test.  Make two 1L starters, one comprised of 100% DME and the other either 50% DME/50% glucose or just 100% glucose.  Pitch lacto into each and compare the results.



On Fri, Aug 23, 2013 at 11:14 AM, Steven P brew-tech@crbeernuts.org (brew-tech@crbeernuts.org))> wrote:
: I've been doing some reading on how Lactic Acid is produced by Lactic Acid Bacteria (LAB).

The link I found at http://textbookofbacteriology.net/lactics_2.html shows that homofermentative LAB including lactococci and pediococci catabolize one mole of glucose (dextrose/corn sugar) into two moles of pyruvate. From there the pyruvate is reduced to Lactic Acid.

Greater than 50% of the available glucose is converted to Lactic Acid.

http://www.brewmorebeer.com/brewing-sugars/ shows typical wort composition at approx 8% Glucose.

This leads me to believe that increasing the percentage of glucose (corn sugar) in the wort would lead to an increased amount of lactic acid. At least down to the tolerance level of the bacteria, which is about PH of 4 or below.

I read many complaints about sour beer not getting sour enough and have to believe if the issue is that the the available glucose to the LAB is getting noshed on by the Saccharomyces before the LAB can get to it.

If glucose is metabolized by the LAB first, then the trick appears to be, instead of taking gravity readings, take PH readings and then boil to kill off the bacteria when the PH hits where you want it. Just like a Berliner Weiss soured in the kettle.

I expect that the total sourness can be increased quickly by feeding the LAB an increased amount of glucose first, then pitching yeast or a mixed culture with additional glucose after the target PH is reached to get a "normal" fermentation.

This should work for all sour beer types. Granted there are other benefits to the traditional long term aging and the hyperattentuation from mixed culture fermentation etc. and the results may end up rather less complex.

Basically the idea is:

1. Add additional glucose and LAB to wort
2. Achieve Sour-er Beer
3. Profit

Or just add liquid Lactic Acid if you want to cheat.

Any feedback is welcome. I just needed to get this out of my head.



Cedar Rapids Beer Nuts Secretary

"Payday came and with it beer"
- Rudyard Kipling