Hi,
I'm looking into experimenting further with malolactic bacteria (Oenococcus oeni, mostly). It's often reduced to "turns tart malic acid into a more mellow lactic acid", but these little buggers do so, so much more. More example, We tried them in mead, made with nothing but honey and pollen, and could easily tell apart the batch done with and without these bacteria, preferring the one with the bacteria. And yet... there was no malic acid in there...
What I'm looking at right now, though, is their metabolization of citric acid into acetic acid and diacetyl. I don't think citric acid is really considered "bad", but the latter two, I believe, are. I've been toying with the idea of using MLF when adding very tart fruits, but before I get started, I want to explore what may occur, to help me in the dosage and such.
The two fruit juices I'm looking to work with are cranberry and japanese quince. For the moment, let's stick with the former.
"The primary organic acids in cranberries are citric, malic, quinic, and L-ascorbic. Mean organic acid content of fresh and frozen berries varied slightly (2041mg/100g and 2035mg/100g, respectively) despite the large differences in individual acids. Malic was the primary acid in fresh berries at 64%. Citric and quinic made up 25% and 11%, respectively. In the frozen berry, citric and malic acids were evenly matched at 42% and 4 1 %, respectively. Quinic remained low at 17%"
Here, I'm thinking of using natural cranberry juice (not cocktails that include water and sugar). Now, if we run on the assumption that we dilute this in a mash, and bring it to an appropriate gravity and pH, we can assume the MLF will convert that malic acid (the main acid) into lactic acid, making it less tart and overpowering. But it will also convert all that citric acid into diacetyl and acetic acid... Yeast can metabolize diacetyl given time... but what about the acetic acid? Is it completely going to ruin the softening of the malic acid? If I put 1L of juice in a 5 gal brew, is it going to taste like vinegar in the end? Does anyone know if quinic acid is metabolized? And does anyone know if any strain can metabolize acetic into something more pleasant?
I was planning to use only Saccharomyces cerevisiae and Oenococcus oeni, but I'm open to adding more friends on the team if needed. My next two experiments with these targeted a sour english IPA and a sour american stout. For both I'll have three versions: one without juice and MLB, one with juice and no MLB, and one with both juice and MLB.
Thoughts, opinions, peer-reviewed articles?
I'm looking into experimenting further with malolactic bacteria (Oenococcus oeni, mostly). It's often reduced to "turns tart malic acid into a more mellow lactic acid", but these little buggers do so, so much more. More example, We tried them in mead, made with nothing but honey and pollen, and could easily tell apart the batch done with and without these bacteria, preferring the one with the bacteria. And yet... there was no malic acid in there...
What I'm looking at right now, though, is their metabolization of citric acid into acetic acid and diacetyl. I don't think citric acid is really considered "bad", but the latter two, I believe, are. I've been toying with the idea of using MLF when adding very tart fruits, but before I get started, I want to explore what may occur, to help me in the dosage and such.
The two fruit juices I'm looking to work with are cranberry and japanese quince. For the moment, let's stick with the former.
"The primary organic acids in cranberries are citric, malic, quinic, and L-ascorbic. Mean organic acid content of fresh and frozen berries varied slightly (2041mg/100g and 2035mg/100g, respectively) despite the large differences in individual acids. Malic was the primary acid in fresh berries at 64%. Citric and quinic made up 25% and 11%, respectively. In the frozen berry, citric and malic acids were evenly matched at 42% and 4 1 %, respectively. Quinic remained low at 17%"
Here, I'm thinking of using natural cranberry juice (not cocktails that include water and sugar). Now, if we run on the assumption that we dilute this in a mash, and bring it to an appropriate gravity and pH, we can assume the MLF will convert that malic acid (the main acid) into lactic acid, making it less tart and overpowering. But it will also convert all that citric acid into diacetyl and acetic acid... Yeast can metabolize diacetyl given time... but what about the acetic acid? Is it completely going to ruin the softening of the malic acid? If I put 1L of juice in a 5 gal brew, is it going to taste like vinegar in the end? Does anyone know if quinic acid is metabolized? And does anyone know if any strain can metabolize acetic into something more pleasant?
I was planning to use only Saccharomyces cerevisiae and Oenococcus oeni, but I'm open to adding more friends on the team if needed. My next two experiments with these targeted a sour english IPA and a sour american stout. For both I'll have three versions: one without juice and MLB, one with juice and no MLB, and one with both juice and MLB.
Thoughts, opinions, peer-reviewed articles?