Insight into the genome of Saccharomyces carlsbergensis

Eureka, another yeast genome got recently published (May 2014) by scientists at the Carlsberg Laboratory in Denmark: Saccharomyces carlsbergensis, the world’s first pure lager yeast used in production since 1883. I would like to review the published article and point out some interesting results. Below the full reference of the paper I am talking about.

Walther A, Hesselbart A, Wendland J (2014) Genome Sequence of Saccharomyces carlsbergensis, the World’s First Pure Culture Lager Yeast, G3, 4:783-793; doi:10.1534/g3.113.010090, http://g3journal.org/content/4/5/783.full

The scientists sequenced the genome using next generation sequencing techniques and compared the genome with Saccharomyces cerevisiae (top-fermenting yeast) and Saccharomyces eubayanus (likely to be a parent of the lager yeasts). Lager yeasts are hybrids and resulted from an interbreeding event between a top fermenting S. cerevisiae yeasts parent as well as a non-cerevisiae parent (likely to be S. eubayanus). This means, the genome of lager yeasts consist of parts of the S. cerevisiae genome as well as parts of a non-cerevisiae parental genome.

Beside S. carlsbergensis, the authors re-sequenced another lager yeast (Weihenstephan WS34/70) for comparative reasons. Lager yeasts can be grouped into group I (Saaz-type lager yeasts) and group II (Frohberg-type lager yeasts). Members of the two groups reflect geographic associations with breweries like group I (Czech and Carlsberg) and group II (Weihenstephan and Heineken). The sequenced S. carlsbergensis strain (CBS1513) belongs to group I whereas WS34/70 belongs to group II. Comparing the two genomes therefore might give some insight into genetical differences between the two lager yeast groups.

Loss of parental S. cerevisiae DNA in S. carlsbergensis

The authors found substantial genome size differences between the two lager yeasts (about 3.5 Mb). A previous investigation showed, the Weihenstephan lager yeast contains two complete parental genomes (S. cerevisiae and S. eubayanus) with some losses at chromosome ends [Nakao et al, 2009]. To address how much of the S. carlsbergensis genome is from S. cerevisiae and S. eubayanus, the authors mapped the obtained S. carlsbergensis genome to the two parent yeast genomes. The comparison revealed, the genome of S. carlsbergensis does not contain information of the S. cerevisiae chromosomes VI, XI and XII (Fig 1, left), harbours some translocated S. eubayanus chromosomes (II, IV and VIII and XV) (Fig 1, right) as well as loss of heterozygosity in some S. cerevisiae chromosomes (Fig 1, right, chromosomes IV, XIII, XV and XVI). This lack of chromosomal information of S. cerevisiae chromosomes VI, XI and XII as well as some loss of heterozygosity is sufficient to explain the smaller genome size of S. carlsbergensis in comparison with the Weihenstephan lager yeast.

F3.large

Fig 1: Pairwise comparison of S. carlsbergensis genome with sub-genome of S. cerevisiae (left) and S. eubayanus (non-cerevisiae) sub-genome (right). Taken from Walther et al, 2014

Summarized, S. carlsbergensis (group I) lost some S. cerevisiae DNA which is still present in the Weihenstephan lager yeast (group II).

Chromosomal map of S. carlsbergensis

The authors generated a chromosomal map for S. carlsbergensis strain CBS 1513 which consists of 29 different chromosomes (Fig 2). Whereas the Weihenstephan lager yeasts harbours 36 different chromosomes (not shown). The individual chromosomes either contain only chromosomal information from the parental S. cerevisiae (parts in blue) or S. eubayanus (orange parts) yeasts or contain information from both yeasts (translocated chromosomes).

F7.large

Fig 2: Chromosomal map of S. carlsbergensis strain CBS 1513. Blue parts represent S. cerevisiae sub-genome, orange parts the S. eubayanus sub-genome. Taken from Walther et al, 2014

To investigate if group I lager yeasts resulted from a hybridization event of two haploid (one copy of each chromosome) S. cerevisiae and S. eubayanus cells, the authors determined the copy numbers of each chromosome present in the S. carlsbergensis genome. If this would be the case, one would expect to find a 1:1 ratio of S. cerevisiae and S. eubayanus chromosomes in the S. carlsbergensis genome.

Surprisingly, the S. carlsbergensis genome seems to be triploid (three copies) with one copy of S. cerevisiae and two copies of S. eubayanus genome (1:2 ratio). The complete S. carlsbergensis genome therefore consists of a total of 47 chromosomes (Fig 2). In comparison, the Weihenstephan lager yeasts is tetraploid (4 copies) with two S. cerevisiae and two S. eubayanus genomes (1:1 ratio).

The comparison showed a clear distinction between lager yeast group I and II with loss of S. cerevisiae DNA in group I. In terms of origin, one may suggest that group I lager yeasts were generated by a fusion event of a haploid S. cerevisiae with a diploid S. eubayanus yeast cell whereas group II lager yeasts originated from a diploid-diploid fusion generating tetraploid group II lager yeasts. Three conserved translocation events in both sequenced lager yeasts may however suggest a common ancestor of both lager yeast groups. And a DNA elimination event may have created group I lager yeasts afterwards.

There you have it. A pretty cool research project. I would like to finish with yet another astonishing result. The authors addressed the level of diversity of possibly one of the original S. carlsbergensis yeast strain isolated by Emil Chr. Hansen in the late 19th century (obtained from Carlsberg bottles of the late 19th century) with the strain deposited at CBS in 1947. The yeasts present in the bottles were identical with the CBS deposited yeast strain. “This suggests very limited evolution of pure cultured yeast strains under industrial fermentation conditions” [cited from Walther et al, 2014]. Pretty cool, right?

I hope you enjoyed reading my short review. Please have a look at the original genome paper as well. I think it is very well written publication. Hope to see some new lager yeast genomes coming out soon.

Bibliography

Nakao Y, Kanamori T, Itoh T, Kodama Y, Rainieri S et al (2009) Genome sequence of the lager brewing yeast, an interspecies hybrid. DNA Res. 16:115-129

Tasting: Mikkeller’s Yeast Series 2.0

Eureka, I would like to share some of my tasting experiences of Mikkeller’s Yeast Series 2.0. The basic idea behind this series was to compare different yeast strains and their effects on the beer’s aroma and taste. I could get my hands on five of the six beers in the series (English Ale yeast is missing) and did a side-by-side tasting.

IMG_1505_cutThe base beer was all the same. In one case, the beer was fermented with a Lager strain, another one with an American Ale strain, yet another one with a Saison strain and two with Brettanomyces lambicus and Brettanomyces bruxellensis respectively. Lets see how they tasted and the individual strain’s impact on the flavor profile.

IMG_1509_cutLager yeast

Aroma: Very hoppy aroma (lots of grapes, fruits). The combination of all the hops used (Simcoe, Nugget, Warrior, Amarillo and Centennial) remind me of Nelson Sauvin hops. No yeast character.

Appearance: Orange, clear, 1 finger white head, nice bubbling.

Flavor: Fruity, nice bitterness level.

Mouthfeel: Medium body, average carbonation level, bitter/fruity aftertaste and a grassy finish

Overall Impression: Rather clean beer (in terms of yeast character). Very pronounced hop aroma and bitterness and a grassy finish

 

IMG_1512_cutAmerican Ale yeast

Aroma: Less hoppy than Lager example. Even a musty component in there. Doesn’t smell clean at all.

Appearance: Orange, clear, 1 finger white head, nice bubbling.

Flavor: Luckily nothing of the weird musty aroma is on the palate. Very fruity beer with a well-balanced bitterness. No typical yeast character.

Mouthfeel: Medium body, average carbonation level, bitter/fruity aftertaste. No grassy finish

Overall Impression: Compared to the Lager version, this beer is smoother in terms of bitterness. The bitterness is well incorporated and there is no grassy finish. However, the aroma in this beer is not as nice. We could not detect any yeast character in this example.

IMG_1513_cutSaison yeast

Aroma: Pine, lots of tropical fruits and citrus and some spicy character (pepper).

Appearance: Orange, clear, 1 finger white head, nice bubbling.

Flavor: Again some fruits and some spiciness in addition.

Mouthfeel: Medium body, average carbonation level, slight bitter aftertaste and a grassy finish and even a bit astringent.

Overall Impression: Slightly different aroma compared to the previous two examples. This time, we could detect some yeast specific character (pepper). This yeast seems to accentuate the bitterness in the aftertaste including a grassy, astringent finish.

IMG_1515_cutBrettanomyces lambicus yeast

Aroma: Subtle hop aroma, no funk…

Appearance: Orange, clear, 1 finger white head, nice bubbling.

Flavor: A bit of a disappointment. Subtile fruity beer with a well-balanced bitterness. No typical yeast character and no funk. Actually a rather clean beer.

Mouthfeel: Medium to low body, average carbonation level, slight bitter aftertaste.

Overall Impression: Not very funky nor very interesting. Average beer. We could not detect any yeast character.

IMG_1514_cutBrettanomyces bruxellensis yeast

Aroma: Wow, now we are talking. There is some Brett funk going on: Wood notes, horse blanket, slight vinegar and the hop profile in the back. This beer reminds me of Cantillon’s Iris with Nelson Sauvin hops instead of the Saaz hops they use. Simply amazing smell!

Appearance: Orange, clear, 1 finger white head, nice bubbling.

Flavor: Unfortunately, not a lot of funk on the palate. Some leathery notes are present. Some fruity notes as well and a well incorporated bitterness. Rather clean beer.

Mouthfeel: Medium to low body, average carbonation level, no bitter nor grassy aftertaste. Hint of tartness reminds of the Brettanomyces in this beer.

Overall Impression: Judging from the smell, the most interesting one in the series for sure. B. bruxellensis really shows itself here. The aroma profile of this beer is surprisingly complex in my opinion. The flavor on the other side is not very yeast pronounced. But the finish is rather pleasant again.

What we learned from this tasting:

Lager strain: Gives a hop forward beer. Clean and very pronounced hop aroma. More pronounced bitterness and a grassy finish.

American Ale strain: Well incorporated bitterness and nice finish. This strain seems to work for more hop forward beers.

Saison strain: Some yeast specific character in the nose and palate. This strain accentuates the bitterness and leads to a grassy and astringent finish. Not really working for me. The spicy character, the grassy thing and the astringency makes it hard to enjoy this beer.

B. lambicus strain: Not a very funky Brett strain. Rather clean beer (compared to B. bruxellensis version). A side note. This doesn’t have to be true for every B. lambicus strain. There are so many B. lambicus strains with different flavor profiles.

B. bruxellensis strain: Lots of Brett character in the nose. But not so much on the palate. Rather clean and smooth beer with a nice bitterness level and no grassy finish.

I will put some efforts into brewing something like the B. bruxellensis beer myself. I am really fascinated about the complexity one can get with a single Brettanomyces fermented beer. Unfortunately, I tried to isolate some yeast from different Mikkeller beers before (brewed by DeProef) but never managed to recover any viable yeasts from the sediments in the bottles. I guess all the DeProef’s beers are pasteurized and therefore no (or a very small) chance to get any living yeasts out of bottles. That’s why I did not bother to isolate the B. bruxellensis strain at all. Thanks for reading, commenting and stay tuned!

#22P Vienna SMaSH

Eureka, another small batch post. Today’s recipe is all about a simple recipe and two different yeast strains. The whole idea behind this recipe was to get some experience with two dried yeasts: Fermentis Safale S04 vs Fermentis Safale US05. To get the most out of the yeasts, I went with a SMaSH recipe. SMaSH stands for single malt and single hop. So basically a recipe with just one kind of malt and one type of hops. This kind of recipe is very common to either test new base malts or new hop varieties. Or in my case to get the flavor characteristics of two different yeast strains. That’s it already for the introduction.

Recipe: Vienna SMaSH
Numbers: Volume [L] 5 (1.3 gal)
Original gravity 11.9°P
Terminal gravity N/A
Color Around 8 EBC
IBU 23 IBU
ABV N/A
Grains: Vienna malt (8 EBC) 1 kg
Hops: Tettnanger (4.2% AA) 7 g and boil for 60 min
Tettnanger (4.2% AA) 5.5 g and boil for 30 min
Yeast: Fermentis S04 vs. US05
Water: Burgdorf Mash: 2.5 L (0.66 gal)
sparge: 4 L (1.06 gal) @78°C (172°F)
Rest: Mash in @66°C (151°F)
60 min @66°C (151°F)
10 min @ 78°C (172°F)
Boil: Total 60 min
Fermentation: Primary 6 days @20°C (68°F) in plastic fermenter
Secondary N/A
Maturation: Carbonation (CO2 vol) 2 vol with sugar
Maturation time 3 weeks

02/13/2011: Smooth small batch brew day. Iodine test was negative after resting for one hour. Then sparged and boiled the wort with the two Tettnanger hops additions for 60 min. Cooled the wort down to 22°C (72°F) and split the wort into two fermentation buckets. Then added the calculated amount of yeast to the fermenters. US05 to one bucket and S04 to the other one.

02/19/2011: Bottled the beer after six days already with an addition of sugars to get to a carbonation level of approximately 2 vol of carbon dioxide. Unfortunately, I did not measure the terminal gravities… Then left the bottles carbonate for another week and stored the bottles in my refrigerator for three weeks.

03/18/2011: Tasting:

US05

Aroma: Slight fruity character (apples) and hint of malty sweetness. No hop character.

Appearance: Yellow-gold colour, poor head retention. The two beers look quite similar.

Flavor: Could detect only some malty character (presumptive from the Vienna malt) and a slight bitterness. No typical yeast character detectable (fruit esters, phenolic etc.)

Mouthfeel: Light to medium body, lively carbonation, short lasting malty aftertaste.

Overall Impression: First, the recipe is exactly what I was looking for: Not a lot of character… In my opinion a very, very boring beer. However, I was not looking for a mind-boggling beer here. The recipe did a very good job. It gave the yeast the opportunity to shine through. Second, how would I describe the character of this yeast in one word? Clean. Clean is a very good descriptive word for this yeast. The yeast ferments very clean and leaves the show to the malts and hops. Sure there was a subtle apple character in the aroma. However, I could not detect any apple character in the flavor. I therefore leave the apple character aside.

S04

Aroma: Light hoppy character. No fruity character.

Appearance: Yellow-gold colour, poor head retention. The two beers look quite similar.

Flavor: Again some malty and bitter character. However, some hoppy character could be detected. And the intensity of the flavors was more pronounced in this beer relative to the one fermented with the US05 yeast.

Mouthfeel: Light to medium body, lively carbonation, medium lasting malty aftertaste. The aftertaste was more pronounced compared to the US05 one.

Overall Impression: Once again, the recipe was in the background. In this case, the malty character was more pronounced compared to the US05. There was even a hoppy character on the palate. I have to keep in mind the gravities here. It might be that the S04 beer finished at a higher terminal gravity than the US05 and therefore the higher terminal gravity might lead to a more pronounced malty character. However, if the S04 finished at a higher gravity than the US05 due to a lower attenuation, the strain still accentuates the malty character. Just by finishing at a higher gravity (less attenuative than the US05 strain). Fermentis describes both strains as medium attenuative.

The S04 yeast strain seems to accentuate the malty and hoppy character of a beer. And does not add any fruity character or any other like phenolic character. A rather clean yeast as well.

To summarize, the US05 seems to be a very clean fermenting yeast. On the other hand, the S04 strain seems to be less clean fermenting and accentuates the hop and malt character of a beer. I would choose the US05 strain for a typical US Pale Ale or an American IPA. The S04 strains seems to be appropriate for English Pale Ales, Mild, Bitter, ESB or English IPAs. If you are not sure what strain to choose, just split a batch and ferment the shares with different yeast strains to see the impact the yeast has on the beer. Cheers!

Wheat yeast comparison results Part 2 (Tasting)

Eureka, this is the second part of the results of the wheat yeast comparison experiment. The background of this experiment can be found here. No further introduction, let’s get straight into the results.

Tasting results

Fig 1: Wheat beer fermented with Wyeast's #3056 Bavarian Wheat Blend

The tasting was done by a group of three people to determine different aromas and flavors of the different beers. The beers were tested in pairs of three over several days to prevent any exhausted palates.

To make it easier for comparison, the following aroma and flavor profiles were evaluated:

Aroma: Banana, phenolic, bubblegum, fruity (apple, citrusy, strawberry, undefined fruits)

Flavor: Citric, phenolic, fruity, bubblegum, banana

The intensity of the individual aroma and flavors were described as following: 5 (high amount), 4 (medium), 3 (little), 1 (hints) and 0 for absent note. The overall impression was evaluated on a scale from 0 to 5 with 5 being the highest rating. At last, the beers were categorized into cloudy/ not cloudy. To evaluate the clarity, the beers were first poured right from the bottles and the clarity was evaluated. Then the rest of the beer was poured including the yeast sediments.

First about the similarities of all the beers. The color of the beers was more or less the same. We could not detect any differences. A typical picture of the appearance can be seen in Fig 1. The mouthfeel of the beers was light to medium with an average carbonation level. The aftertaste was short to medium lasting and the balance (sweet to bitter) of the aftertaste was more on the sweet side than bitter one. Differences are discussed below.

I mentioned that I did two fermentations for each of the strains. I turned out that some of the replicates had a different head stability and some had signs of oxidation. We therefore poured each replica side by side and evaluated both. If there were some off-flavors detectable with one of them, we just used the one without any flaws for the results below. Luckily, there was at least one flawless replica for each of the strains.

I will first talk about the flavor and aroma profile of the different yeast strains and then talk about the clarity and the overall ratings.

#3068 Weihenstephan

Fig 2: Wyeast's #3068 Weihenstephan aroma/flavor profile

I used this yeast strain in the three batches I did as a control yeast to determine any differences between the three batches. But the beers from the three different batches fermented with the #3068 Weihenstephan yeast all had the same profile: huge banana (Fig 2). Nothing else! The differences between the batches were very minimal. This concludes that the beer of the three batches were very comparable. And this allows to compare the yeasts from the different batches with each other since there are no differences in the basic beers.

Wyeast describes this particular strain to give banana and clove notes. Reasons for the lacking clove note are discussed at the end of this post. All in all a very beautiful yeast. The beers were all cloudy. No surprise since this is a low flocculating yeast strain. Pretty refreshing and the banana really belongs into such a beer in my opinion. Overall rating: 4.

#3056 Bavarian Wheat Blend

Fig 3: Wyeast's #3056 Bavarian Wheat Blend aroma/flavor profile

The beer fermented with the #3056 Bavarian Wheat Blend had a distinct phenolic and fruity (strawberry) flavor (Fig 3). Wyeast describes this strain to be estery and phenolic. This beer was cloudy (medium flocculating yeast strain). Reasons for the lacking clove note are discussed at the end of this post.

I already tried this particular strain before and had the strawberry notes in there as well. This strain is not my favorite one because of the strawberry note. This strain could be used in a beer where a strawberry note is desired. Maybe in a fruit infused wheat beer? Overall rating: 3.

#3638 Bavarian Wheat

Fig 4: Wyeast's #3638 Bavarian Wheat aroma/flavor profile

Fermenting the wheat beer with Wyeast’s #3638 Bavarian Wheat leads to a fruity beer. We could not assign a fruit to the detected fruit aroma. Maybe a lichi note? But lot of fruits and bubblegum in the flavor (Fig 4). Wyeast’s aroma/flavor description for this strain are apple, pear, plum esters in addition to a dominant banana character. The esters are complemented nicely by clove and subtle vanilla phenolics. The lacking banana component could be due to different pitching rates or fermentation temperatures. The beer was cloudy (low flocculating strain).

I am a bit surprised about this strain because of the lacking banana notes compared to the #3068 Weihenstephan strain (both fermented at the same temperature). Maybe this strain produces less banana esters than the #3068 Weihenstephan? This strain is not my favorite one as well. I still prefer the #3068 Weihenstephan. Overall rating: 3.

#3333 German Wheat

Fig 5: Wyeast's #3333 German Wheat aroma/flavor profile

First, the aroma and flavor profile of this beers was lower than all the other strains (Fig 5). We could detect some banana, fruity and again, strawberry notes. And fruits and banana in the flavor. There were some sherry notes as well and the beer was pretty dry compared to the others. This could be due to a higher attenuation level of this strain compared to the other strains.

Wyeast’s description: This yeast strain produces a beautiful and delicate balance of banana esters and clove phenolics similar to the popular Wyeast 3068. We could not detect any phenolic notes in this beer. And in our opinion, the banana/ phenolic balance was not similar to the #3068 Weihenstephan strain. Once again, reasons for the lacking clove note are discussed at the end of this post. This beer was not cloudy. Wyeast recommends this strain for Kristallweizen because of its high flocculation.

Well, the strawberry note does not fit my palate very much. And the subtle aroma and flavor notes do not help this beer as well. Maybe a different fermentation temperature could change this. Overall rating of 3.

WB-06

Fig 6: Safbrew's WB-06 aroma/flavor profile

Now, how do the dried yeasts compete against the liquid yeasts? This beer had a very fruity and apple driven aroma (Fig 6). And some fruity and citric (lemony) notes in the flavor. Safbrew describes this yeast to give a subtle estery and phenol driven flavored beer. Lets say the fruity notes we picked up belong to the subtle estery note. But we could not pick up any phenolic notes. Once again, reasons for the lacking clove note are discussed at the end of this post. This beer was clear (although stated to be low flocculating). Although the attenuation of this particular strain was above average (see first part of results), the beer was not drier compared to the other beers. Overall rating: 2. Very odd flavor profile in my opinion. And not a really refreshing beer either.

One additional goal of this whole experiment was to determine whether Wyeast’s #3068 Weihenstephan strain is the same as the WB-06. Well, this can hereby be confuted. The 3068 gave an overpowering banana note, the WB-06 did not.

Danstar Munich

Fig 7: Danstar's Munich yeast aroma/flavor profile

There were just some sherry notes and some signs of oxidation detectable (Fig 7). There should be banana notes as stated by Danstar. But we could not pick up any banana notes at all. The beer was clear (medium to high flocculating strain). I will not further comment this strain because of the possible oxidation of this beer. I assume that there was a problem in the fermentation process or bottling in both replica.

Burgdorfer Weizenhefe

Fig 8: Burgdorfer Weizenbierhefe aroma/flavor profile

Now the last typical wheat yeast strain. This one was isolated from a local wheat beer. And there were some banana, fruity and strawberry notes again (Fig 8). But none of these aromas in the flavor. The beer was cloudy. This strain is less interesting than some of the other strains in the experiment. Overall rating: 2.

So far for the typical wheat yeast strains for a typical German wheat beer. Lets move on to some other wheat yeast strains.

#1010 American Wheat

Fig 9: Wyeast's #1010 American wheat aroma/flavor profile

The first strain we discuss is Wyeast’s #1010 American Wheat strain. We could pick up huge fruity and citrusy (lemony) notes in the aroma and the same notes in the flavor (Fig 9). This beer was cloudy. Wyeast describes this strain as following: produces a dry, slightly tart, crisp beer. Ideal for beers when a low ester profile is desirable. Well, the beer was kind of dry but the ester profile was in my opinion a bit higher than stated. But a really refreshing beer indeed and something different from the banana and phenolic yeast strains. This strain could be a really good one for lighter beers for the summer such as a Pale Ale. And the lemon note is really nice. Overall rating: 3.

#3942 Belgian Wheat

Fig 10: Wyeast's #3942 Belgian Wheat aroma/flavor profile

And the last strain in this experiment was the Belgian Wheat strain. Well, what would you expect from a Belgian yeast strain? Phenolic, phenolic and again phenolic notes. And that’s more or less what was in this beer. And some fruity notes in the aroma (Fig 10). Wyeast describes: moderate esters and minimal phenolics. Apple, bubblegum and plum-like aromas blend nicely with malt and hops. Well, the tasting panel was not that far away from Wyeast’s description. I have to say that I really enjoyed this particular brew. It was still very refreshing but had a very different flavor profile than a typical German wheat beer. This beer was again cloudy (medium flocculating). This strain is my favorite non-German wheat yeast strain. A pretty cool strain in my opinion. Overall rating: 4.

Overall discussion

The descriptions from the suppliers were very similar to the taste panels opinion. Sometimes, the beers had less or none phenolic notes although stated by the suppliers. This difference could be due to a different fermentation temperature or different pitching rates. In fact, at the same time as I was writing this post I came along an interview with an employee from Wyeast. The interview can be found here. In my opinion one of the best and most educational interview ever. Check it out. Owen Lingley mentions that underpitching of wheat yeasts can lead to a more prominent banana character. Overpitching leading to a more phenol driven beer. And I guess this is the answer to the lacking phenolic notes in the beers because I intentionally underpitched all of the beers. And the results kind of confirm Owen’s statement. One message to take home: if you want huge banana character, underpitch. If you want phenolic notes in your wheat beer, then overpitch. Increasing the temperature will lead to an increasing ester production. Maybe underpitching and raising the temperature will further increase the banana character?

Another flavor was determined several times: strawberry. I already mentioned that I detected such a flavor in a previous wheat beer which was fermented with the #3056 Bavarian Wheat Blend. But we could detect strawberry notes in the #3333 German Wheat and the isolated Burgdorfer Weizenhefe as well. I have no idea about the background how this flavor got in there.

What about my favorite strains? Well, my favorite strain before this experiment was the #3068 Weihenstephan strain. The #3068 Weihenstephan is still my favorite strain but there are some other strains which are really interesting. There is the #3942 Belgian Wheat and the #1010 American Wheat strain that fascinated me the most. And there is the #3638 Bavarian Wheat which I will use in another wheat beer soon.

Summary

The goal is achieved, the different yeast strains are described. And the WB-06 seems to be a different yeast strain than Wyeast’s #3068 Weihenstephan yeast strain. Another thing the effect of pitching rates and fermentation temperatures. After a yeast strain is selected, the character of the particular yeast strain can further be influenced by the pitching rate and the fermentation temperature.

So, this was a really huge experiment. It took me three batches and a lot of bottling time to get the different beers into bottles. And then came the fun part, the evaluation of the different flavors and aromas. Then another huge working load to blend all the data together and at last, write about it. Now I am really fed up with wheat beers for a while…

Please feel free to comment below. I really appreciate all the comments and thoughts.

Wheat yeast comparison results Part 1

Eureka, I finally did it. After several hours of tasting, collecting data and other stuff, I am now able to post the first results of my wheat yeast comparison experiment. The experimental design is already posted in a previous post. Todays post is all about yeast performance, the tasting of the different beers will follow in the second part. I split the results in two parts to make it easier to read and because the tasting part is not yet written. Lets begin.

Result and discussion

As the Cooper’s yeast showed molds in the starter, the yeast was excluded from the experiment.

Batch analysis

Batch Nr. 1: Volume: 20 L (5.3 gal), Original gravity 14.0°P, Sudhausausbeute = 62%
Batch Nr. 2: Volume: 30 L (7.9 gal), Original gravity 14.0°P, Sudhausausbeute = 59%
Batch Nr. 3: Volume: 40 L (10.6 gal), Original gravity 13.8°P, Sudhausausbeute = 67%

The original gravities and the efficiencies (Sudhausausbeute) of the three different batches were quite similar. The used brewing technique seemed to be more or less consistent over three batches. I already observed a higher efficiency for higher batch sizes in other brews before.

Yeast analysis

The terminal gravities were measured by a refractometer and transformed into a terminal gravity [°P] by use of a table. The apparent attenuations are shown in Fig 1. The uncertainty was calculated by the standard deviation and shows the region of the mean value with a certainty of 95% (equals two standard deviations).

Fig 1: Apparent attenuation levels of different wheat yeast strains compared with stated attenuations of the yeast suppliers. n = 2 (except for the #3942 (n=1) and #3068 (n=3)). No numerical attenuation levels stated for WB-06, Danstar Munich and Burgdorfer Weizen.

As shown in Fig 1, all the yeasts reached the apparent attenuation as specified by the manufacturers. The measured apparent attenuations seemed to be slightly higher than the specified values. Further information about the #3068 and the huge error bar follow below. The measurement of the #1010 American Ale and Burgdorfer Weizen were the same in both fermenters thus no error bar. The #3942 Belgian Ale yeast fermented just one batch, thus n=1 and no error bar as well.

The highest attenuative yeast was the dried yeast WB-06, the lowest the isolated Burgdorfer wheat yeast from a bottle. It can be concluded that a wheat yeast has an apparent attenuation of about 75%.

The attenuation levels of the #3068 Weihenstephan in the three different batches compared with the specified attenuation level from Wyeast is shown in Fig 2. The #3068 was used as a reference yeast strain in all the three batches.

Fig 2: Apparent attenuation levels of the #3068 in the three different batches

It can be shown that the #3068 in the first and second batch differ significantly. The attenuation in the second and third batch were quite similar. To compare the attenuation level of the #3068 with the other yeasts, the author used the average of the three batches and used the standard deviation for the calculation of the error bars. This is the reason for the big error bar in Fig 1 for the #3068 Weihenstephan yeast. One explanation could be that the fermentation was not over yet and the terminal gravity was not at its lowest point. Another, the source of the yeast. The yeast for the first batch was isolated from a previous batch of wheat beer. The yeast for the second batch was used from the first one, and for the third one from the second.

One goal of the experiment was to find out, if the #3068 Weihenstephan is indeed the same yeast as the dried WB-06. Comparing the apparent attenuation of the #3068 and the WB-06 does not lead to a clear answer: Comparing the #3068 from the first batch with the WB-06 shows no difference in attenuation between the two yeasts. Comparing the second, third batch fermented with the #3068 and the WB-06 shows a clear difference. Comparing the specified attenuation of the #3068 with the WB-06 shows a clear difference as well. The manufacturer of the WB-06 specifies the WB-06 yeast to be highly attenuative. The attenuation of Wyeast’s #3068 is stated to be between 73- 77%. Assumed that a high attenuation is in the region of 85%, this would mean, that the attenuation levels of the two yeasts differ significantly.

The author concludes, through the comparison of the different average-attenuation levels of the two yeasts, that the attenuation level of #3068 Weihenstephan and WB-06 differ significantly.

To summarize, the apparent attenuations of the yeasts tended to be higher than the specified values. The WB-06 yeast reached the highest attenuation, the isolated Burgdorfer wheat yeast the lowest. A wheat yeasts attenuates in the region of 75%. The #3068 attenuated differently in the three batches. The #3068 Weihenstephan and the WB-06 had not the same apparent attenuation levels. Thus it is quite probable that the two yeast strains are indeed not the same.

That’s all about the wheat yeast performance results. I am a bit surprised about the different attenuation levels of the WB-06 and the #3068 Weihenstephan strain. Maybe the drying process of the yeast could influence the attenuation level in some way? The final word will be spoken after comparing the two beers in a tasting. As already mentioned, the tasting results will be posted in a different post soon. I still figure out how to present the different results in a comfortable way. Stay tuned.

#28 Helles Weizen

Eureka, after the Belgian yeast experiment post, now the countdown for the big wheat yeast comparison. And I start with my wheat recipe which I already brewed for at least four times. This particular recipe was the first batch for the wheat yeast comparison experiment.

Recipe: Helles Weizen
Numbers: Volume [L] 20 (5.3 gal)
Original gravity 13.6°P
Terminal gravity 1.9- 4.1°P (different strains)
Color Around 3 EBC
IBU 10 IBU
ABV Around 5.9 %
Grains: Wheat Malt (3 EBC) 2.6 kg
Pilsner Malt (3 EBC) 2.1 kg
Acidified malt (5 EBC) 0.1 kg (added at 53°C)
Hops: Hallertauer (8% AA) 6 g and boil for 60 min
Hallertauer (8% AA) 6 g and boil for 30 min
Yeast: #3068 Weihenstephan, #3333 German Wheat, #3638 Bavarian Wheat, #1010 American Wheat, WB-06
Water: Burgdorf Mash: 12 L (3.2 gal), sparge: 19 L (5.1 gal) @78°C (172°F)
Rest: 4 steps Mash in @47°C (117°F) without acidified malt, 20 min @ 45°C (113°F), add acidifiec malt, 15 min @ 53°C (127°F), 30 min @ 63°C (145°F), 40 min @ 72°C (162°F), 10 min @ 78°C (172°F)
Boil: Total 60 min
Fermentation: Primary 12 days @ 18°C (72°F) in a plastic bucket
Secondary N/A
Maturation: Carbonation (CO2 vol) 4 with 22 g of cane sugar per 2 L (0.53 gal)
Maturation time 2 weeks @20°C (68°F) and 3 – 4 weeks @4°C (39°F)

04/22/2011: Brew day. All went as planned. Filled up ten plastic buckets with 2 L of wort (0.53 gal) each and added the yeasts. Used two different buckets for every yeast (for backup if one fermentation does not finishes as it should).

Fermentation vessels for the wheat yeast experiment

05/04/2011: Bottled the beers. What a workload! Used about four bottles for every plastic bucket.

June/July 2011: The tasting begins. Results will be posted in the wheat yeast experiment results.