A Tale of Two Yeasts

By Craig Flewell and Jeff VanDreal  

The Inspiration  

Tom’s Brew Shop employees Craig Flewell and Jeff VanDreal decided to try an experiment. What would happen if they mashed and boiled a batch of  beer, then split it in two and pitched each half with a different yeast? Only one way to find  out, so they tried it! While Jeff is a retired diplomat focused more on the art of brewing,  Craig, as a retired engineer, was determined to pursue the scientific method in this  experiment. Between them, they figured they’d have every angle covered.  

The Recipe  

Our brewers decided early that the beer twins should be a lager and an ale. They also decided to brew at Jeff’s downtown Denver apartment due to on-hand equipment redundancy, despite the small batch (typical yield is about six quarts of finished beer)  limitation that location dictates. Since Jeff had had some recent success with brewing both a red ale and a red lager, both based on Tom’s 1 Gallon Red Ale kit recipe, our brewers opted to follow (loosely) that same recipe.  

The grain bill consisted of 75% Root Shoot English Pale Ale malt, 10% Proximity Crystal 60  malt, 10% Weyerman CaraRed malt and 5% Proximity Dextrin for head retention. The hop bill consisted of equal shares of Willamette and East Kent Goldings.  

As for the yeast, due to temperature control issues with Jeff’s set up, they decided to use Propagate’s Lager Kveik and Hornindal Kveik.

Brew Day

Jeff’s set-up entails brew-in-a bag in a pot on the electric stove. Our two brewers mashed  in with eight quarts of water at 150 degrees F. The mash temperature varied from a low of  147 to a high of 160 over the course of the 30 minute mash. They then mashed out for 10  minutes at a temperature up to 174 degrees, and sparged with three quarts at 168 degrees.

Analysis

Water to grain ratio: 
8 quarts / 6 lbs = 1.33 quarts / lb. (customarily about 1.0 to 1.2 quarts / lb. )

Mash efficiency:  
Total water => 2 gal for mash + .75 gal for sparge = 2.75 gal (11 quarts)  Total grist = 6.0lbs  
Water loss within mash => 2.75 gal – 2.3 gal = 0.4 gal.  
0.4 gal / 6.0 lbs = 0.07 gal / lb  

Mash/mash out/sparge was followed by a team effort to squeeze the grain bag to  recover as much sweet water as possible resulting in a very low mash absorption rate.

Pre-boil gravity was measured at 1.055 with 2.3 gal  
2.3 x 55 = 127 gravity points  
Total gravity points in the grain bill is 206  
Mash efficiency = 127/206 = 66%

The efficiency figure, while low for 3 vessel systems, is in the normal-ish range for  BIAB systems of 60-70%, which supports the idea that, for well modified grains, a 30  minute mash gets the sought after conversion accomplished, and saves time.

The boil was also limited to 30 minutes, with ½ of the Willamette going in at 30 minutes and  the other half at 20 minutes. Irish Moss was added at 15 minutes, ½ of the Kent Goldings at 10 minutes, Whirlfloc at 5 minutes and the other half of the Kent Goldings at flameout. Once removed from heat, the wort was stirred vigorously for ten minutes to simulate a  whirlpool. Then the entire batch was cooled via ice bath to 72 degrees F. The glass hydrometer reading for the wort stood at 1.062.

The boil loss and cooling shrinkage resulted in a volume loss of about ¼ gal, which  is tiny, but does reflect about 10% of the starting boil volume. For comparison, on  Craig’s 10-gallon system, he typically loses 1.5 gal (15%) per hour of boil, plus an  additional 4% due to cooling.

At this point, our brewers split the wort roughly in half and poured it into two separate  fermenters. Into one fermenter, along with a red Tilt floating hydrometer, they pitched the  appropriate amount of the Hornindal Kveik yeast. Into the second fermenter went a green  Tilt and the Lager Kveik yeast. Both fermenters were sealed tightly and placed side by side in a closet. 

Fermentation

Both Tilts read 1.064 one hour after pitching, but the lager yeast took off almost  immediately. At the 12 hour mark, the lager (green Tilt) was well ahead of the ale.  However, the ale (red Tilt) caught up by the morning of day 2, then slowly overtook the  lager. While the ale drifted down over the first 14 days, the lager remained stable as of day  5. 

Bottling

Twenty days after brew day, it was time to bottle. In order to ensure uniform dosage of  priming sugar given the uncertainty of exactly how much was in each fermenter, our  brewers decided to use PopCulture’s Pop Shots carbonation drops. First, they siphoned off the ale into a bottling bucket, then filled sterilized bottles for a yield of 80 ounces. The  final gravity reading from a glass hydrometer was 1.021 for an ABV of 5.4%. After cleaning  and re-sterilizing the bottling equipment, they then transferred the lager via the bottling  bucket into sterilized bottles totaling 128 ounces. The final gravity reading here was 1.020  on the glass hydrometer, resulting in an ABV of 5.5%. 

While the difference in gravity was a single point, it is nevertheless interesting that the  yeast which started so much faster than the other also ended up with an ever so slightly  higher attenuation. It is also worth noting that while the attenuation of both yeasts – 68%  for the lager, 66% for the Hornindal – was lower than expected (“high 70s”), performance  was consistent with Jeff’s previous experience brewing at home. 

Analysis:  

Not hitting the advertised attenuation mark is not unusual, but is worth some  thought for possible improvement going forward.  

Mouthfeel – The final gravity of these two beers were 1.020 & 1.021, but if the yeast  had attenuated to the advertised level, would have hit about 1.015. These figures  may not seem like much, but to a beer enthusiast, the experience could be  sufficient reason for ordering a 2ed pint vs not finishing the 1^st.  

Higher final gravity does change the sweetness of the beer, while some styles  welcome the sweetness, others may not benefit.  

Sweetness could be the result of non-fermentable sugars in the wort, or an  incomplete fermentation. One possible cause of the former is too high of a mash  temperature. If the average mash temp. was lowered by around 5F, the quantity of  non-fermentable sugars would decrease (and the quantity of fermentable sugars would increase), aiding the yeast to reach maximum attenuation potential. Actively  adding oxygen to the wort prior to pitching yeast would increase chances of a  complete fermentation. 

Tasting Notes

After a minimum of 12 days of bottle conditioning in Jeff’s closet at room temperature, it  was time to sample! Not surprisingly, both beers looked identical in color and clarity, but  the lager had a slightly better head and carbonation. While the lager was light and crisp,  the ale showed more complexity in terms of flavor profile and mouthfeel. The ale featured  fruitier and sweeter notes, with a somewhat more intense aroma. One taster noted buttery  notes in the ale and a hint of sulfur, while the lager offered a breadier taste.