Kettle Sour Question

[somenerve]

We're in the process of planning out our first ever kettle sour. Just want to know if the lactobacillus will consume any appreciable portion of the fermentable sugars in my wort? Should I assume I'll get a lower O.G. than the same recipe without the lacto? If so, how much lower?

[Thirsty_Monk]

Bill,

Kettle souring will lower gravity about .5 Plato in my process.

Good Luck

[somenerve]

Bill,

Kettle souring will lower gravity about .5 Plato in my process.

Good Luck

Thanks Leos!

[UnFermentable]

I am not sure the post really answered the question. Is Thirsty_Monk saying that the FG will be 0.5 plato lower than a non soured version of the same recipe? Or is he saying that the souring process (in his case) takes the OG down 0.5 Plato (prior to Saccharomyces addition)? I think he is stating the latter, with which I agree. The former would be a bit more subjective.

Different strains of lactobacillus behave differently, with some being considered homofermentative, and some being heterofermentative. They can all produce lactic acid by way of metabolizing glucose, however some will produce 85% or better lactic acid (Homo) and others produce ethanol and lactic acid (Hetero). Some strains can metabolize oligosaccharides which could theoretically effect your FG differently than a Saccharomyces strain might.

Basically lactobacillus will ferment the same sugars as the yeast will, however some strains can also metabolize some sugars/carbohydrates that most strains of Saccharomyces yeast cannot. Brevis, Delbruckii and Plantarum tend to be the most widely used strains of lactobacillus in beer, but there are other possibilities. Traditional beers would have been inoculated at the same time (theoretically) making the yeast and bacteria compete for resources. In kettle souring, you are giving preferential treatment to the bacteria and "freezing" the process when your desire amount of metabolism has been completed. You then allow the yeast to clean up whatever is left.

[Thirsty_Monk]

UnFermentable. I usually get 0.5P drop from when wort is chilled to 100F till i boil wort after i am done souring.

It is not always the same. I do not use pure strain of bacteria but rather take the bacteria that is on the grain husk.

Your milage may very.

[fatback]

Hi Bill,

.5 Plato drop from post-mash to pre-boil seems about right in my process as well. Pure pitches of Lacto Delbruecki or Lacto Pantarum seem to result in a bit less sour (less plato drop...around 3.4ph-3.5ph) than a nice pitch of Greek yogurt (around 3.3ph) in my experience. I have also tried the new Lallemand Sourvisae and that makes an insanely sour beer (3.0 ph) without the need for the souring step. Just pitch it like pure yeast and it sours and ferments in one step. This method makes it difficult to know how much alcohol is in the finished product though (apparently lacic acid is similar gravity of alcohol).