Author: Matt Del Fiacco

I’ve primarily utilized dry yeast as a back-up when I don’t have the time to make a starter or something goes wrong. As such, my yeast fridge is regularly stocked with several packets of both Safale US-05 and Saflager W-34/70 to cover my typical range of styles. I recently found myself in possession of a packet of a seemingly novel Fermentis yeast called Safale K-97 German Ale, the “K” presumably indicating its use for Kölsch. I couldn’t find much information about K-97 outside of the manufacturer’s description of it as a fairly clean fermenter that’s perhaps a bit more expressive and lends slightly more ester character than the popular US-05. With limited user reviews, I was naturally curious and in the interest of adding another yeast to my repertoire or even finding a more interesting US-05 replacement, I decided to compare this novel yeast strain to the popular Safale US-05!

| PURPOSE |

To evaluate the differences between two beers fermented with either Safale US-05 American Ale yeast or Safale K-97 German Ale yeast.

| METHODS |

I wanted to brew something clean with moderately low bitterness to let the yeast express itself and settled on a moderately hopped Pale Ale recipe.

Handshake-Schmändshake Pale Ale

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.5 gal 60 min 34.9 IBUs 3.7 SRM 1.050 1.012 5.0 % Actuals 1.05 1.014 4.7 % Fermentables Name Amount % Canadian 2-Row (Canada Malting) 10 lbs 93.02 Vienna Malt (Weyermann) 12 oz 6.98 Hops Name Amount Time Use Form Alpha % Bru-1 8 g 60 min Boil Pellet 15 Bru-1 8 g 25 min Boil Pellet 15 Bru-1 28 g 5 min Boil Pellet 15 Bru-1 36 g 3 days Dry Hop Pellet 15 Yeast Name Lab Attenuation Temperature Safale American (US-05) DCL/Fermentis 77% 59°F - 75°F Notes Water Profile: Ca 80 | Mg 2 | Na 10 | SO4 125 | Cl 62

I began my brew day by heating the full volume of water for my no sparge batch and adjusting it with minerals to hit my target profile.

As the water was heating to strike temperature, I weighed out and milled the grains for the batch.

Once my water was at strike temperature, I lowered my brew bag into the kettle, gave it all a quick stir to ensure the grain was distributed, and then double checked to make sure I’d hit my intended mash temperature, which I ended up being a bit over.

About 15 minutes into the mash rest, I pulled a small sample or sweet wort, chilled it down, then took a pH reading to ensure I’d hit my target.

Once the mash was complete, I pulled the bag of grains out of the kettle and started heating the wort, adding the initial bittering addition as soon as a boil was reached then adding the other additions at the times listed in the recipe.

Once the boil was complete, I chilled the wort and pulled a gravity sample which showed I was about .002 over my intended OG.

I racked equal amounts of wort to separate PET carboys and set them in my fermentation chamber to finish chilling to my desired pitching temperature of 64°F/18°C.

Once there, I re-hydrated the yeast and noticed the K-97 appeared visibly more active than the US-05 after about 15 minutes.

I pitched the yeast and aerated the beers before letting them settle in for fermentation. After 12 hours, the US-05 beer was just starting to show signs of fermentation while the K-97 batch had taken off.

At 10 days into fermentation, fermentation appeared done for both beers so I took hydrometer measurements that showed what appeared to be a potentially negligible 0.001 SG difference.

I dry hopped both beers, let them sit at fermentation temperature for another day, then cold crashed overnight and fined with gelatin. After 3 days at 35°F/2°C, I transferred the beers to kegs, which were placed in my cool keezer and burst carbonated.

After 12 hours, I reduced the gas to serving pressure and let the beers condition another week before collecting data, at which point a difference in appearance was immediately noticeable.

| RESULTS |

A panel of 21 people with varying levels of experience participated in this xBmt. Each taster, blind to the variable being investigated, was served 2 samples of the beer fermented with Safale US-05 and 1 sample of the beer fermented with Safale K-97 in different colored opaque cups then instructed to select the unique sample. While 12 correct selections would have been required to achieve statistical significance, a total of 15 tasters (p<0.05; p=0.0004) chose the different beer, suggesting participants could reliably distinguish a beer fermented with US-05 from one fermented with K-97.

The 15 participants who made the correct selection in the triangle test, still blind to the variable in question, were instructed to compare only the 2 different beers and asked about their preference. In all, 7 tasters reported preferring the US-05 beer, 5 said they liked the K-97 beer more, and 3 had no preference despite noting a difference.

My Impressions: I was easily able to tell these beers apart just by appearance, as the beer fermented with US-05 was much clearer than the K-97 beer. I was also able to identify the unique sample consistently over a series of triangle tests. To my palate, the beer fermented with K-97 was a bit more classically expressive and had a bit more character than the US-05, giving it in edge when it terms of personal preference. I also appreciated how the K-97 held a persistent head and left nice lacing on the glass. However, there was nothing wrong with the US-05 beer, I enjoyed drinking both just fine.

| DISCUSSION |

In my research of the yeasts compared in this xBmt, it seemed most of the people with experience using Safale K-97 felt it was similar enough to Safale US-05 as to be basically interchangeable, hence I was pretty surprised to find participants could reliably distinguish between beers fermented with either strain. Also, I observed many participants making their selection rather quickly, suggesting they were fairly confident in their choice. This coupled with my own experience leaves me with the impression US-05 really is different than K-97, which I guess isn’t terribly shocking.

In follow-up conversations with tasters after they completed the evaluation, I learned that the distinguishing characteristic of the K-97 fermented beer for some was that it seemed “inappropriate” for a Pale Ale, which I’m guessing can be attributed to the subtle unique yeast character it contributes. While preference for either beer was basically split, I’m compelled to believe mine for the beer fermented with K-97 was at least somewhat due to my awareness of the variable, as I’m a big fan of German styles.

A quick note on some reports I’ve read from others claiming K-97 imparts a Hefeweizen-like character– that’s not really how I’d define it. The beer I fermented with it certainly was unique and more characterful than the US-05 fermented beer, but not in a way that would leave me convinced it was a Hefe. Although different, the beer was still clean with a subtle ester character I expect in styles like Kölsch.

While I won’t be going out of my way to keep my fridge stocked with dry yeast, this experience was eye opening and I look forward to using K-97 German Ale yeast in a proper Kölsch or perhaps Altbier in the future to see how it contributes its own unique character!

If you have experience with either of these yeast strains or thoughts about this xBmt, please don’t hesitate to share in the comments section below!

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