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CDH
02/03/07 05:19 PM  
Target temperatures for bug propagation
I've got a beer that I've planned to turn into an Oud Bruin. It got fermented back in October with S-33 dry yeast which left lots of residual carbs for bugs to munch upon. I've just added the dregs from a few bottles of a previous Roeselare beer, so now I'm wondering what temperature will most benefit my newly added bugs. Last time I put the beer through the whole Roeselare process from start to finish and it took 9 months... I'm hoping the right temps might speed the bugs up some.

Any microbiological advice to had here?

FWIW, my recipe was as follows:

2.5 lb. Belgian pale

2.5 lb. Belgian Pilsner

2 lb. American Vienna

1 lb. American Munich

.25 lb. Belgian CaraMunich

1 lb. Flaked corn

.25 lb. Torrified wheat

.5 lb. Dextrine malt (Cara-Pils)

.25 lb. Belgian aromatic

.25 lb. Belgian Special B

.5 lb. Flaked oats

.25 lb. Honey Malt

1 oz each of Willamette and debittered at 70, and again at 15.

CDH
02/05/07 10:21 AM  
Re: Target temperatures for bug propagation
Well, to follow up on my own query, since nobody appears to have anything to add...

The Raj Apte paper indicates that Lactobaccilli are happy between 60 and 150F... so I'm taking that as a pointer that warmer is better for souring bugs. The sacch. cerv. are clearly done with it and have been for months, so I'm going to put the keg it's souring in up beside the radiator and let it get good and warm.

Has anybody figured out how much of the Roeselare character is Brett vs. Lacto? What would the sweet spots be for encouraging one, the other or both to do their thing?

I wonder how much warmth will transfer into a keg resting up against a hot water radiator. 5 Gallons of heat sink vs. lots of flowing hot water intermediated through cast iron and stainless steel... I doubt it would get anywhere near 150... but I wonder if it might pasteurize the brett if it gets too warm.

SteveG
02/05/07 10:45 AM  
Re: Target temperatures for bug propagation
I can't really help on the temperature thing, but I can comment on Roeselare character Brett vs. Lacto.

I think you will find the blend needs to be worked up for a generation or two then it will enjoy another few generations of great performance before deteriorating. The stuff in that blend all have very different life cycles and thus fall out of synch quickly (I hope I am describing this correctly). My first Roeselare beer was pretty mild in terms of the souring effect, Al played with it, adjusted the blend balance and handed it back. It performed beyond my expectation for two beers and did OK on the third, though by then sourness was starting to over-dominate. So I think even if you have a guy like Al to help you out, the best he can do is create a window of opportunity that will close fairly quickly.

Oh, about pasturizing warmth (your last question) - I hope so! I wanted to halt the progression of a brett strain that came out of a Fantome bottle in a barley wine I made (this was just a week or so ago). Again, I consulted Al, I was thinking of heating it to 150 for some amount of time, but I did not know how long. He did some quick research and recommended 140F for 60 minutes.

Al B
02/05/07 11:19 AM  
Re: Target temperatures for bug propagation
Generally speaking, bacteria multiply and sour faster than yeasts when competing for nutrients, especially as temperature goes up. However when Brett flavors devleop, they can overwhelm the characteristics of everything if left alone (much depends on the strain, nutrients etc.).

Judging from your recipe, there may be a good amount of dextrins for souring bugs. To get an understanding of whats going on with a mixed inoculum, I recommend tasting periodically, take pH readings, specific gravity (and add a thermometer). Alot will be learned. If the brew is off target for whatever, you can always blend with a fresh batch. Good luck.

Al Bacteria

CDH
02/05/07 02:45 PM  
Re: Target temperatures for bug propagation
Thanks for the thoughts.

In your experience, what is the composition of the bottle conditioning sediment in Roeselare beers?

Does it vary with time? If so, which beasties are hardier, the lacto or the brett? My bottle sediment is coming from a very successful Rodenbach Alexander reproduction that got brewed in April 2005, spent that particularly hot summer outside in a shed, spent the following fall/winter in my 55 degree basement meeting some sour cherries, and got moved into bottles about a year ago to naturally condition.

Will time/heat/acidity/etc have knocked out the balance of beasties? All I'm hoping for is the brett/lacto souring process, and I'd rather not cut open my last smack pack of Roeselare at this moment, and I don't have anything else going right now that could benefit from it.

Al B
02/06/07 07:39 AM  
Re: Target temperatures for bug propagation
<< In your experience, what is the composition of the bottle conditioning sediment in Roeselare beers?>>

I assume you mean from WY Roeselare blend. After examining the morphology of that mixed culture, I found at least one Sacch., lactobacillus, and one brett. Of course this is a minimum account of real flemish reds aged in barrels. But does the job.

<<Does it vary with time? If so, which beasties are hardier, the lacto or the brett? >>

Well, thats a complex question. Alot has to do with the populations of each bug, types of complex sugars/dextrins, temperature, and oxygen. With respect to the R blend, I notice lactic sourness before Brett. As time goes by, Brett character becomes evident, then overpowering, and probably more acidic. Wyeast says the more times the culture is used, the more sour the beer become. Well, that makes sense since bacteria multiply very fast in respect to yeasts.

<<Will time/heat/acidity/etc have knocked out the balance of beasties? >> Time. Heat makes things act faster up to a point - like pasteurizing.

I really suggest to sacrafice one of those bottles and see where it lies. The complexity of mixed cultures are tough to predict.

 
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