Hops and Lactobacillus - not IBUs?

[storunner13]

So...just thinking about the 'common knowledge' (or at least common after reading Wild Brews and other 'Funk' blogs) that Lactobacillus is 'IBU-phillic' - or, is unable to reproduce when in an environment with high IBUs.

Do we know that it is the IBU contribution of hops which inhibits Lactobacillus?

Here's what I'm reasoning--

Lambics use aged hops which have very little bittering potential. However, they use large quantities to inhibit Enterobacter and Lactobacillus. It is suggested (or perhaps known empirically) that the other compounds in the hops contribute to inhibiting these organisms.

Therefore - 1oz of aged hops would not be as inhibitory as 3oz of aged hops..

So, using .5oz of hops with high AAs could contribute the same number of IBUs as 1oz, albeit inhibiting Lactobacillus less.

It's very possible I'm missing an important idea about the alpha acids, beta acids, humulone, cohumulone, essential oils, or some other part of the picture which is skewing how I'm looking at the inhibitory aspects of hops.

*Cross Posting on Babblebelt*

 

[Nateo]

The Lacto from the labs, like White Labs and Wyeast don't deal with IBUs well. Some kinds of wild Lacto have much higher tolerances for high IBUs.

Whether or not it's actually the bitterness that messes up the Lacto I couldn't say.

 

[spearko520]

http://www.scientificsocieties.com/jib/papers/1993/1993_99_5_405.pdf

 

[Guess42]

The portion of the aged hops that inhibits lacto I believe is the oxidized beta acids. The beta acids are not soluble without the age induced oxidation.

Having said that many people have noticed lactobacillus being inhibited by alpha acids.

 

[ryane]

The portion of the aged hops that inhibits lacto I believe is the oxidized beta acids. The beta acids are not soluble without the age induced oxidation.

Having said that many people have noticed lactobacillus being inhibited by alpha acids.

Yes its the beta acids that are useful in lambic brewing, but alpha acids are inhibitory as well, a friend of mine working on MFC's used a hop extract (ordered from sigma aldrich) at one time to selectively grow certain bacteria and inhibit others

 

[Guess42]

Meant in his response to his last statement. Btw what is an MFC? Also, would be interested in what he was trying to grow and inhibit.

@ op: Should have finished my thought process. The higher aa hops will probably give more preservative powers than the low aa ones when both are young. This is because the beta acids are not yet soluble in the beer until they have aged (oxidized). Not sure on the relative ba conc. of hops to say that aged high aa would have more than aged low aa ones.

 

[ryane]

MFC = microbial fuel cell

 

[Oldsock]

Yes its the beta acids that are useful in lambic brewing, but alpha acids are inhibitory as well, a friend of mine working on MFC's used a hop extract (ordered from sigma aldrich) at one time to selectively grow certain bacteria and inhibit others

Agreed. To add to that, I have also read that beta acids are less soluble than alpha acids, which is most likely part of the reason lambics are boiled so long. Although volatilizing their iffy aromatics is most likely part of it as well.