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08/28/13 03:43 PM  
"Acidic vs Acetic"
I've always heard people judge a beer based on it being acidic vs acetic. I know acetobacter creates the acetic acid and so assumed then that lacto/pedio create "acidic acid". Then I learned that lacto/pedio both create lactic acid, so why don't people say "lactic vs acetic"? Also, I feel like there is a difference between beer that uses lacto vs pedio as their bacteria. Is there actually any difference between the acids they produce?
Gabe H
08/28/13 07:37 PM  
I think some brett strains in some conditions make a lot more acetic than most people give them credit for. I just tasted an 8 month old Bug County lamebic last night and it's got a ton of citric from some of the odd bretts in there.

I feel like there is a difference in lacto and pedio, but I've never read anything to indicate the lactic acid they make is somehow different, but pedio seems both smoother and more complex.

I can't find the article, maybe it's a thesis(?), but I found an interesting paper on the results of a study showing that most people can't tell the difference between lactic, malic, citric, and acetic.
08/29/13 09:07 AM  
There most certainly is a difference between products of different species of lactic acid bacteria but it's not the lactic acid that's the big different. Its the other metabolic byproducts. There are different isomers of lactic acid but both pedio and lacto produce both isomers. I think some strains produce both and some may only produces one isomer. There shouldn't be any difference when talking of lactic acid flavor, because lactic acid is lactic acid. However because they are all genetically different each species of lacto or pedio will all produce different accompanying compounds which contribute to flavor. It's not the flavor of the acid that's different it's the other compounds produced.

More specifically it's got to be a homofermentive vs heterofermentive difference. While the generally held consensus is homofermentive only produce lactic acid the truth is that lactic acid is only primarily produced. There's no CO2 production with homofermentative but they do produce other compounds along with lactic acid from glucose. Depending on the other sugars present it would affect it's final products and we should be able to taste them dependent on their flavor threshold.

Heterofermentive strains can produce both lactic, acetic, and ethanol. Again it depends on the strain, conditions and sugars. Some strains are faculatively heterofermentive which means they pretty much always act that way, some are dependent on the sugars and the conditions.

So its sort of like saccharomyces vs brettanomyces, I think. One produces primarily ethanol but the brett can produce ethanol and considerable amounts of acetic acid compared to saccharomyces. Other than that the flavors associated with each species is very strain dependent and dependent on the fermentation conditions.

I think the acidic vs acetic is a issue of people not knowing. Acidic I would say is a general term for sour. Vinegar is acidic, pickles are acidic, sour beers and yoghurt are acidic. However, vinegar and pickles are acetic, while yoghurt and beer is primarily lactic. I think it's a case of knowledge and/or old ways of describing beer from when homebrewing started.
08/29/13 10:48 AM  
Good information, thanks.

It makes sense that each is creating lactic acid and then also a whole bunch of other stuff. I find pedio to be a much cleaner strain. Even saying that I know it is always used in conjunction with brett, which means another set of variables. Maybe I just prefer the combination of pedio and brett over simply lacto? (Russian River vs Cascade)

I assume there is also a difference in how much lactic acid the two strains make?
08/29/13 11:06 AM  
I am in your camp with presence of brett. I tried two different Cascade beers and they're sour with an metallic bite (think hard water in an old metal canteen). I'm not a fan and think they greatly lack complexity. Plus at $20 a bottle I'll spend my dough on homebrewing ingredients. I think if they just added brett they'd be better off. Ultimately if I want a sour I'll go with a mixed culture of everything and pitch it in the beginning. I'm a complexity through diversity kind of guy with sours. Its funny to say this but I am sort of against clean ale strain then souring culture. I think you end up with a snoozer of a sour, boring and little complexity. At least if you go ale yeast then souring culture use something that's estery so the souring microbes have something to work with other than just complex sugars. It's easy to see brett's affect if you take a strong estery/phenolic tripel and add brett to the bottle. Over time brett smooths the beer out and it loses the high notes. The other interesting I've found through the years is brett ultimately will break down some chill haze proteins. I've had beers never hit the fridge except the week I drink them since bottling. They pour as if they've been filtered.
Gabe H
08/29/13 04:36 PM  
So if all lactic acid is equal, does beer soured with lactic acid rather than bacteria taste bad because it's missing the by-products of bacterial fermentation?
08/30/13 09:48 AM  
That's got to be the issue. The 88% lactic acid we can purchase and put in beer (like Festina de Peche) is biologically produced, likely from pediococcus, and then purified probably through distillation. My gut tells me there's something from the processing that remains in a higher concentration while the other metabolic byproducts of lactic acid fermentation are driven off. It's like the difference between fermented pickles and pickles with just adding vinegar. Or the difference of fermented saurkraut or just simply a sour brine. The fermentation process makes so much more than the product we're ultimately after.

It'd be interesting to make a wort sour half with bacteria and the other half with lactic to an equal acidity. So you'd have to look at pH, and titratable acidity to come up with the correct v/v % of lactic acid in the beer. Then subject each beer to GC/MS analysis to see how different their profiles end up. I suspect the naturally soured wort will be much different than the 88% lactic acid soured wort. The controls would certainly have to be same wort, and same yeast. Of course the sugar concentration and variety would ultimately end up slightly different due to the lactic acid fermentation. Time would also have to be a control and the non-bacteria wort would have to be tested to give a fair reading after the same amount of conditioning allowing any biotransformation of the lactic acid and any other compounds to occur with the yeast present. So it'd also be highly interesting to see the same test done in these different ways.

1. saccharomyces only with lactobacillus vs saccharomyces and 88% lactic acid

2. Saccharomyces and brettanomyces with lactobacillus vs the same with 88% lactic acid

3. Brettanomyces and pediococcus vs the same and 88% lactic acid

4. Mixed culture consisting of 1ea Saccharomyces, brettanomyces, lactobacillus and pediococcus vs the same with 88% lactic acid.

The little experiments would be a bit boring but for in order to have controls and limit variables it has to be that boring. You can't design an experiment and expect measureable outcomes for comparison with highly diverse cultures unless it's just an observation you're after.
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