Posted March 21, 2014
We employ four full-time beer scientists (yes, that’s a real job) in our quality assurance/quality control lab. Each of them has different specialties utilizing various methods and tools in the objective analysis of beer. I’ve previously talked about our gas chromatograph that shows us the chemical makeup of our beer. This piece will focus on a tool we use to identify the presence of specific beer spoiling microorganisms, our Real Time PCR.
The process begins with a Boulevardian from the brewing or lab crews taking a sterile sample from a fermentation vessel, bright beer tank, or package. The sample port, keg valve, or bottle is flamed to ensure that a clean sample is pulled. Once the sterile sample has been collected, it’s delivered to our lab where our microbiologist takes custody of the sample.
Using sterile methods, a compound that will allow the DNA of potential beer spoilers to separate from the beer is added. The resulting mixture is heated to near boiling before being centrifuged to cause a very distinct separation of the beer and any potential DNA. Finally, a a probe compound is added. This probe compound will bind with any DNA present allowing the machine to detect it. Once loaded, the PCR begins a process of heating and cooling the sample to replicate any DNA present. If you’d like some super technical information regarding this process, go here. If there happens to be a beer spoiler present in the sample, even in tiny amounts, the replication and then identifying process will allow our microbiologist to determine not only the genus of the beer spoiler (lactobacillus for example), but also the species, lactobacillus brevis being a possibility. Being able to accurately identify the microorganisms that are present in a sample informs our lab crew as to what the next step is. In the case of a beer like Saison-Brett, which we intentionally inoculate with brettanomyces, a positive test for brettanomyces results in high fives all around. A sample of Pale Ale that reads positive for a common beer spoiler like lactobacillus lets our lab know that this tank needs to be watched for continued growth and a more aggressive cleaning/sanitation regiment is necessary before the tank is filled again.
[caption id="attachment_4358" align="aligncenter" width="300"] This graph shows the temperature fluctuation during the heating and cooling series. Each green dot represents a time when the machine is actively reading the sample.[/caption]
It’s quite rare that we find beer spoilers in our beers at Boulevard, but having such a powerful tool at our disposal is key to evaluating our cleaning/sanitation procedures to protect the integrity of our beer. I love sour beers and Saison-Brett, but we want to keep our other beers “clean” as we’re not looking for wild yeast or bacterial influence in the final flavor profile.
- Jeremy Danner, Ambassador Brewer