Lacto and IBU :)

[Lele]

Hi everyone, and greetings from Italy and sorry for my English
For my next beer, I want to make an experiment, putting grape that is fermenting and brettanomyces in beer wort. This will be one of my first sour beers, and I haven't understood yet very well the relationship between Lacto and IBUs. Lactos are present on the grape's skin and I don't want to inhibit their action. So I ask you two advices:
1) how many IBU can Lactos tollerate? I know that some Lacto is more IBU-tollerant than others, but I don't know how many IBUs their can tollerate.
2) a beer with a few IBUs (for exemple <5 or 10 IBUs) will bee too sweet or this isn't a problem because of Brettanomyces that are able to ferment dextrins as well?
Thanks

 

[dmtaylor]

I think hop mass matters much more than IBUs. However I have had a high-IBU IPA get accidentally infected by Lacto. The finished beer was plenty sour. Based on my experience, I think hops (or "IBUs"?) do not inhibit Lacto as strongly as some sources suggest.

I think if you want to ensure Lacto activity, you should pitch some real Lacto from a commercial culture, or from sour cream or yogurt or a known source. From just the grapes themselves, I do not believe there is a guarantee that Lacto will take hold.

You are correct about Brett. A finished beer with Brett will usually not be very sweet, and especially with grapes, it should dry out significantly due to the amount of simple sugars present.

Good luck.

 

[Lele]

Thank you for the advices
Maybe you're right about IBUs and Lacto. I've read that, with Lacto, it's better not tu use more than 5 IBUs, but your experience tell me that I can use more IBUs. However, for the first time, I'll try not tu use more than 15 IBUs, just in case
I don't know if somebody else has different experience about it.

But for me, the big question is about Brett and IBU. I know that many sour beer recipe have only 5 IBUs. I thought that this ins't a problem because Brett are able to ferment almost anything. But an Italian brewer said to me that 5 IBUs are too low, and the beer risks being not balanced. So...I'm a little confused: is it true or not? And, if this brewer is right, why many sour beer recipes have only a few IBUs?

 

[dmtaylor]

Balance can come in a variety of ways. Bitterness or IBUs are just one way to balance the beer. Sourness is another way. Herbs would be another way. I have made sour beers without any hops at all, which used fruit or herbs or both. I would say they were still in balance based on the sourness. I have also made kvass which had no hops, fruit, or herbs. That beer I was not very fond of, because it wasn't sour either, so it did seem out of balance.

So, I don't think you need a lot of IBUs to be in balance. Sourness or herbal character can also be credited for "balance".

 

[jfolks]

I saw a presentation by Pattie Aron of BSG/Rahr at NHC in Minneapolis - she presented on the science of IBUs - and she presented some evidence that may shed some nuance into the issue of lacto's "IBU intolerance." Correct me if I'm wrong, but you characterize lacto as "IBU intolerant." However, a study Pattie referenced suggests that lacto isn't actually IBU intolerant, but is actually hop acid intolerant. As seen in the slide below, Peacock found that storage temperature affects the alpha acid of aged hops (and thus the iso-alpha acids in the resulting beer), but had minimal impact on achieved IBUs in the resulting beer. We all know that age/temp/O2 exposure impact alpha acid of hops. But given that driving down alpha acids in hops (ex: aging them) only marginally impacts achieved IBUs in the beer, can't we conclude that lacto's "IBU intolerance" is actually a misnomer - and that in fact lacto is intolerant to hop acids? (Granted, there is a correlation with alpha acids and IBUs when using "new" hops - so telling listeners to keep IBUs low seems like a good simplification/strategy). (Note: Patti did not extrapolate the Peacock results to the lacto issue I've raised - this is my interpretation of the Peacock results. So I asked her about it and she discussed the chemistry of the issue and ultimately suggested my theory was correct (she went on to say that lacto is actually intolerant to alpha, beta, and iso-alpha acid - and aging hops changes the chemistry on these hop acids in a way that lacto can then tolerate. Go to the 49 minute mark to hear my Q and her A: https://s3-us-west-2.amazonaws.com/...s/Bitterness-And-The-Ibu-Whats-It-All-About-1
link to the slide deck: https://s3-us-west-2.amazonaws.com/...Bitterness-and-the-IBU-Whats-It-All-About.pdf)View attachment 579847

 

[RPh_Guy]

I wouldn't trust wild Lacto to sour a wort with more than 5 IBU. I would use 0 IBU.

Sour beers don't need hops because the acidity balances the sweetness, and usually there isn't much residual sugar. You can easily add a hop tea to provide IBU after fermentation if you desire, or dry hop for just flavor/aroma.

@dmtaylor I'm wondering how you got so lucky finding an extremely hop-tolerant Lacto, or perhaps it was actually Pedio or a lactic acid yeast. Did you have it identified?

@jfolks Aged hops still inhibit Lacto, so there must be something that's inhibitory but not affected by aging.

Lambic brewers use aged hops specifically to inhibit Lacto. Pedio, which is more hop tolerant but slower, does the large majority of lactic acid production.

I think we're on the same page

 

[dmtaylor]

@dmtaylor I'm wondering how you got so lucky finding an extremely hop-tolerant Lacto, or perhaps it was actually Pedio or a lactic acid yeast. Did you have it identified?

I wouldn't call it "lucky" --- I was very PO'd about it. It tasted very lactic. (And I'm BJCP Certified and love yogurt and sour cream so I believe I know what lactic tastes like.) But I'm not exactly sure which organism did the job. What I can tell you is that there was a very thin layer full of white curd-like material on the top of the fermentation, so I racked out from under that prior to packaging. Does this help identify the organism? It was probably about a 50-IBU beer so it was not short on hops, but it was just as lactic sour as any sour Lacto beer I have ever had (which is a lot).

 

[RPh_Guy]

Sorry about the beer but I'd love to have something that sours with so much hopping.
If it was indeed Lacto you were very unlucky to get such a both resilient and aggressive strain of it.

Unfortunately you can't really identify the organism based on the presence or appearance of a pellicle.

 

[Lele]

OK, then I'll keep it under 5 IBUs.

From just the grapes themselves, I do not believe there is a guarantee that Lacto will take hold.

I know that an Italian brewer makes a beers putting 20% of fermenting grapes, and nothing else. I taste it and it's delicious
I think that Lactos are very present on the grape, but I'm not sure. Somebody else has try this "experiment"?

 

[RPh_Guy]

I'd wager there's plenty of Lacto on the grapes but that's just an educated guess.

I prefer to use known Lacto cultures though because I generally want consistency and predictability.