[Editor's note: we are proud to hire on University co-op students, and try to provide opportunities to contribute to research activities while at Escarpment Labs]
Taste is king. The phrase was deemed to be the most important answer on a midterm for a functional foods class. The example they used was the cold medication Buckley’s; it tastes awful but it works. The taste of a product is everything when a consumer is debating on purchasing or trying the food or beverage. The taste of the ingredients is debated upon when formulating new products. There are many factors that influence the taste of a food or beverage product such as an individual's tasting palate, the ripeness of a fruit or the spices used.
In the case of the beer industry two different yeasts, with very different aromas and tastes, can be used to create a single beer where the flavours and aromas projected from each strain pair extremely well together and create the ultimate beer.
During my time at Escarpment Labs I was tasked with investigating how the fermentation temperatures of a blend impact the stability of it, and testing whether a Kveik yeast blend is more stable than a Saison blend. We get asked about the stability of the Kveik and Saison blends fairly frequently, so we thought it would be a good idea to put it to the test!
We can investigate the stability of yeast blends thanks to the different appearance of some strains in the blends on WLN agar. Here, one strain stains darker than the other making it possible to differentiate between the two.
This project investigated how two different fermentation temperatures changed the stability and ratio of yeasts in the Old World Saison Blend and Hornindal Kveik Blend, each being a blend of two strains. The temperatures selected for the project were 20 ºC and 25 ºC (these were the incubators I had access to). The experiment was carried out from Generation 0 to the end of Generation 5. Each generation at each temperature was conducted in triplicate to assist with the validation of the results and all cell counts were performed in duplicates to assist with the accuracy.
The Old World Saison Blend was selected for use because one of the strains in the blend contains the active form of the STA1 gene and one does not. The STA1 gene allows the strain to produce the glucoamylase enzyme which enables it to catabolize more complex sugars present in wort that would otherwise not be broken down by non diastatic (STA1-negative) strains.
Cell counts were performed on the starters and the Hornindal and OWS were created with a 50/50 mixture of their respective strains of yeast. Each generation was left to ferment for 14 days. Fermentation gravity checks were performed and slurry from the previous generation was used to inoculate the next generation. The remaining slurry was diluted and plated onto WLN plates, one for each of the replicates of each generation, temperature and blend. The benefit of the WLN plates is that different strains look different on this agar on the basis of uptake of the bromocresol green dye.
The Kveik blend appears to be more stable than the Saison blend when repitched over multiple generations.
In the graphs demonstrating the percentage of each strain above, the composition of the Hornindal changes slightly at 25 ºC but remains stable at the new percentages for several generations after the change. While, the HB fermenting at 20 ºC remained stable at a roughly 50/50 mixture. It was interesting to us that the Hornindal blend was more stable at 20 ºC vs. 25 ºC, since kveik yeasts are traditionally used at a hotter temperature.
The OWS at 25 ºC and 20 ºC demonstrated minimal stability after generation 1. In both graphs the OWS#1 appears to dominate the mixture. It is likely this is due to this strain being more aggressively diastatic than the other strain.
The results indicate that the kveik blend is more stable than the saison blend. It's fascinating to us that kveik mixed cultures can stay so stable over time, when many other yeast blends lose stability. We are hoping to apply this to improving yeast blends in the future and ensure they are more consistent from batch to batch.
Unfortunately we were not able to follow this up with a sensory study, but that would be a great next step!
Shelby Stein is one of our current Co-Op students, responsible for assisting the QC and production teams. She is currently studying Biomedical Toxicology at the University of Guelph, with the hopes to one day be a Forensic Toxicologist. Shelby is great at parallel parking, dodging poles and signs like its her day job.
Shelby heads back to University of Guelph in September 2020 - best of luck Shelby!