[a10t2]

I'm going to start brewing some sours this spring/summer (on purpose, for a change). Just wondering what people's experiences have been with growing up a culture from a small amount of malt, as opposed to ordering from one of the yeast labs. What are the odds of getting a Lactobacillus-dominated culture on the first try? Any issues with flavor stability over time? If I do get something I like I want to be able to store it in the fridge and reuse it at least a few times.

[kramerog]

I understand that acidifying your wort to a pH of 4.5 will prevent clostridium butryrica and other undesirables from taking hold.  If you do that I think your chances of success are very high.

[tschmidlin]

I haven't done it, but I know a pro brewer locally who sours his mash for some beers.  He said it is really important to block out all of the air to keep it from getting nasty.  That's not the first time I've heard that either, it seems to be a common belief.

[Jimmy K]

The main trick is that lactobacillus grows best around 110F, so keep those cultures warm during growth. I've never heard of a sour mash going wrong, so I think it is pretty safe. Wort pH is probably low enough to at least inhibit most everything else until the lactobacillus gets going, which doesn't take long.  Not sure about storage, but I imagine it would be stored like any other starter.

[kramerog]

Crooked stave acidfies their mash to a pH of 4.5 when doing sour mashes.  I heard that on a podcast with the brewer.

[erockrph]

Crooked stave acidfies their mash to a pH of 4.5 when doing sour mashes.  I heard that on a podcast with the brewer.

IIRC, it sounded like the first time Chad sour mashed he ended up growing some butyric acid producing bacteria, and it took a really long time for the Brett to break it down to palatable levels. He started acidifying to pH 4.5 after that experience.

[reverseapachemaster]

I've done quite a few sour mashes. More specifically, I do what people call sour worting. I've never had an issue with off flavors in the beer. I do limit oxygen exposure as well.

[kramerog]

Another thing I remember is that lacto is active at temperatures above 125 F, but not much more while other beer bacteria generally are not.  So it would be advantageous to pitch your grains say at 126 F and allow the wort to slowly cool to 110 F to give your lacto a head start.

[Jimmy K]

Another thing I remember is that lacto is active at temperatures above 125 F, but not much more while other beer bacteria generally are not.  So it would be advantageous to pitch your grains say at 126 F and allow the wort to slowly cool to 110 F to give your lacto a head start.

Not sure where you heard that, but this is from SigmaAldrich.

Lactobacilli have a generation time ranging from 25 to several hundred minutes. The optimal growth temperature ranges from 30 to 40°C, although some thermophilic strains grow well and have highly activated metabolism at temperatures around 45°C.

45C is 113F. Unless perhaps they will simply survive 125F while others will not.

[kramerog]

Pitching at 126-128 F does not kill the other beer bugs.  They are just inactive in that range while lacto is active allowing the lacto to get a head start. 

[a10t2]

OK, I pitched a handful of crushed malt (Global Pils, FWIW) into a liter of 8.5°P wort, purged the growler with CO2 and sealed it with an airlock. It's in the fermentation chamber at 40°C. I guess we'll see what happens.