This post is about beer, but in addition, this post is about the microbiology of beer, specifically the microbiology of the genus Saccharomyces. I am a microbiologist by trade, so there will be several posts throughout this blog concerning the organisms responsible for the production of beer and other fermentation products. This is the first in a series of posts about different Saccharomyces species, the end product of a fermentation with related species. My hope is that I will be able to explore the molecular biology / microbiology of beer and to and repeat this format with Brettanomyces strains (and other microorganisms) in the near future. If you don’t like biology, you can skip to the beer / brewing portion of this post below.
Saccharomyces cerevisiae is the yeast strain used in the majority of ale production around the planet. If you are a homebrewer or a professional brewer, S. cerevisiae is likely your #1 employee. There are definitely other species of bacteria and yeasts used in fermentation (various Lactobacillus, Pediococcus, and Brettanomyces species — these will be discussed in future posts) but if you make an ale, you likely use S. cerevisiae, but it is not alone though. The genus Saccharomyces has 7 recognized (single genome) species; S. arboricola, S. cariocanus, S. cerevisiae, S. eubayanus, S. kudriavzevii, S. mikatae, and S. paradoxus. In addition, there are two more hybrid species, S. pastorianus (S. cerevisiae plus S. eubayanus) and S. bayanus (S. uvarum plus S. eubayanus). S. pastorianus is the “lager” yeast species responsible for fermentation of the majority of the world’s beer. It is believed to be a fusion of S. cerevisiae and S. eubayanus. S. pastorianus and S. cerevisiae are responsibie for >99% of the beer production on the planet, so you are likely familiar with these strains if you have ever had a beer.
Today, I’d like to discuss another species from Saccharomyces genus, S. paradoxus. S. paradoxus is a close relative of S. cerevisiae even though on the genomic level the two species diverge greatly, morphologically and physiologically they are quite similar. In fact, using typical yeast differentiation strategies, it is nearly impossible to tell the difference. S. paradoxus grows slower at higher temperatures than S. cerevisiae . S. paradoxus is a high attenuating strain as well as ethanol and acid tolerant. As far as I can tell, it seems to have the same fermentation profile as most S. cerevisiae strains.
I decided to start with this strain for a few reasons. First, I have to start somewhere…second, S. paradoxus has no known pathogenic properties, so it should be relatively safe. Third, it is pretty closely related to S. cerevisiae so my assumption is that it should behave similiarly to the various strain of S. cerevisiae that I’m used to working with.
Today is a special brew day, this beer will be brewed by my wonderful wife, Krissi…she wants to learn the ropes so I will be assisting her on this one. Take it away love.
Batch # 2014.03
5 Gallon Batch
Brew date: April 6th, 2014
Bottling Date: May 22nd, 2014 — 48 twelve ounce bottles
ABV: 5.0% (estimated)
SRM: 2.5 L (estimated)
IBU: 14 (estimated)
9 lbs of Pilsen
1 lb of wheat
Slightly undershot the mash temp on this one but not by much. Mash was carried out in about 4 gallons of water with a pH stabilizer (5.2) for 1 hour. The mash temp was 149 F at the beginning, I was hoping for a few degrees higher but it will work. Sparge was at 165 F with 5 gallons of water. About 8 gallons was water was collected after the sparge.
A total of a 70 minute boil on this one. Nothing too complicated here. The whole point of this beer is to be as simple as possible, as boring as possible. I want a blank canvas to see what the yeast is about…no complicated hop, malt, or anything character. Bring on the yeast.
1 ounce of Czech Saaz (AA% 4) at the beginning of the boil.
Again, basically nothing.
A 1 liter culture of S. paradoxus was grown in YPD media at 30 C with shaking to aerate the culture. The culture was chilled and the supernatant was poured off. The remaining yeast was resuspended in water and stored in a Falcon tube. No cell count was attempted (I was being lazy)…the culture was pitched into the fermenter on April 6th, 2014…fermentation was underway within a day. This might have been a slight underpitch. Krausen fell after 5 days, fermentation continued (thin layer on the top of the carboy and airlock activity). Beer was allowed to ferment out for two weeks.
So, never underpitch…especially if you don’t know how a yeast is going to behave. This beer stalled…hard….the fermentation stopped at 1.030 and sat there. I was able to get it going again by swirling the fermenter to kick the yeast up into solution, but these guys were likely suffering from dilution shock and crashed out half way through. The fermentation picked back up after a few hours and the gravity continued to drop for several weeks.
This beer ended up being one of the longer fermentations in recent memory, definitely the longest fermentation of a 5% beer I’ve done since I did a bunch of 100% brett beers a few years back. I think these guys are a little slow and a little fragile. The 1.030 wort (stalled) did not taste like anything except sugar water. This might just be a high flocculating strain as well though, falling out of solution easily. Something to consider.
This beer did not go to kegs. It was bottled into 48 twelve ounce amber bottles (standard stuff) and carbonated in bottle with table sugar to two volumes of carbon dioxide.
Beer served in a stemmed glass. Beer is yellow and almost completely clear with moderate carbonation, small and medium bubbles, decent white head, moderate to low head retention.
Aroma is interesting. It sort of smells like a strong white wine or a champagne with slight fruity notes and a little lemon. There is a mild breadiness to the aroma as well. Since there are no hops in this beer to speak of, all of those aromas are coming from the yeast. Smells pretty good, it is a little subtle overall but good.
Beer is light in body and effervescent on the palate. Again there is a mild citrus and some funk to it. Definitely has a vinous quality to it with a little bit of breadiness and milk sulfury funk. It is a good beer, the lemon shines through and combines with this nice grape quality. I wish it were less bready overall but having it dry out in the bottle a little definitely helped with that.
I’m going to keep drinking these over the next several months and I will likely post an update in 6ish months regarding how this particular beer is aging. I think it is a nice novelty though and worth the look.
I really enjoyed this experiment, I’m looking forward to testing additional yeast species.
Possible improvements (for future batches):
I am excited to try other yeasts from this genus and play with fermentation conditions as well. I hear that East Coast Yeast is planning on offering this in the future. This beer turned out good, nice fruit character to the beer overall. I’m pretty pleased. I am going to brew another beer with this strain though and change two things, first I’m going to pitch more cells….underpitching with such a nice flocculating strain is not a good idea. And second, I want to lower the temperature on the fermentation. That might take care of some of the breadiness.
This is going to eventually be part of a bigger suite of posts as I delve into a greater variety of yeast strains and species throughout the life of this blog but currently I am not planning on making any additional odd yeast beers in the immediate upcoming future. I would like to remake this beer though with some different malts or different mash temperatures and control the fermentation temperature better. I think this species deserves a little more attention than it has gotten. I would love to brew with the soon-to-be available commercial example of this yeast. Since mine was obtained through a genetic stock center, I’m not sure how the genotype differs from the others that are being used currently in the homebrew community.
Actually brews that are coming up…more saisons. There will be a few more flower saisons this year (chamomile, galaxy, and a couple of others), the garden is underway so hopefully a chile beer from the garden will be coming up soon as well. A Russian Imperial stout is next along with several different saisons, as well as a bunch of sours in the works. A Chinook and Cascade IPA just went into a fermenter so there’s that as well.
“Since the most ancient times, all men, and particularly those who endeavored in the practice of medicine, have brought closer together two natural phenomena of capital importance: illness or fever and fermentation.” — Louis Pasteur