From The Bruery:
Last week we outlined why sour beers are such a pain in the butt to make in Sour Barrel Aged Beer 101- Challenge Accepted! This week, thanks to the power of the interwebz we can answer some of your questions you posted on our Facebook & Twitter. If you have a sour bottle handy, now's probably a good time to pop it open!
Here are some of the common questions related to brewing sour barrel aged beers, answered by Tyler King, our Senior Director of Brewing Operations who we're pretty sure you know by now, and the lovely Jessica Davis, our brilliant Quality Specialist.
Jess has been on our team for several months now and we are thrilled to have on board with her years of experience in SCIENCE! She knows how to do all kinds of weird things in our fancy lab, and she has been handling the tremendous task of keeping our yeasts and beers happy & healthy. If you ever see her around the Tasting Room, give her a sanitary high-five! 
What kind of special handling do you have to deal with for yeasts for sour beer?
Jess: We must keep everything separate, especially any equipment that is porous. I have separate glassware for Brettanomyces and I autoclave everything to ensure sterility and purity of the culture. Some sour yeasts require more time to propagate. It is also possible to even store them for long periods at ambient temperature with no agitation and then reinvigorate the culture later when you need it.
What special steps must be taken when brewing sour beers?
Tyler: Cleanliness & Sanitation. There's a huge risk when brewing these types of beers and you don't want them contaminating your non sour beers. The unique strains used for sour beers can wreak havoc on non sour beer production if cross contamination occurs. 
How can cross contamination occur?
Jess: Cross contamination can occur by several means. It is most important to understand that these organisms, unless at a particular concentration, cannot be seen by the naked eye. If your hands, a piece of equipment or just simply the air comes in contact with a sterile surface it can become contaminated. 
As far as the brewing goes, how are dark/red/blonde sours different?
Tyler: We use malts and fruit to get different colors which usually means different flavors. The style of beer usually determines how we make it, but usually we just do what we think is going to make the best tasting beer! 
What sour yeast strains do we use?
Jess: We mainly use several species of Brettanomyces, but we also dabble in using strains of lactobacillus and pediococcus that are types of beer souring bacteria. 
What makes the Hottenroth kind of sour different from Rueuze kind of sour?
Tyler: The malts, hops, water and yeast/bacteria used. Hottenroth is mostly a Brettanomyces and Lactobacillus fermentation, while Rueuze can have up to eight different strains in it. On top of that, Rueuze is barrel fermented & aged while Hottenroth uses stainless steel. 
How does time affect these yeasts in our beer?
Jess: Most souring yeasts and bacteria are opportunistic. They either hide until the time is right to start reproducing or grow so quickly they are able to out compete other organisms for food and space. Most are also able to metabolize sugars that Saccharomyces cannot.
For example, if you look at growth curves of Saccharomyces with Brettanomyces in the same beer you will see a spike of cell concentration early on of the Saccharomyces, then once the Saccharomyces has depleted its resources Brettanomyces will kick in and start eating up what is left (which is mainly cellobiose).
If you were to throw some bacteria in the mix you would see an even more interesting shift of cell concentration of each strain as the pH decreases and alcohol content increases, producing some very interesting aromas and flavors. 
How quickly can a homebrewer make a sour batch in glass or stainless steel?
Tyler: This can be done pretty fast, probably in a month or so. Bigger beers (like a Flemish Red) will benefit from age though, as Brettanomyces can take around 180 days to fully develop.
What tips do you have for a homebrewer looking to brew their first lambic?
Tyler: Read Wild Brews by Jeff Sparrow!!
Thanks for your questions everyone. Next up we'll look at the intricacies of cellaring, then packaging sour barrel aged beers. Start thinking about what you want to know. 
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