Author: Marshall Schott

A few months ago, Robb Burden, owner of Southern Hills Homebrew Supply, announced that he’d combined 59 packs of 25 different strains of almost expired yeast into a 5 gallon batch of starter wort, the slurry of which of he planned to split up and dole out to interested homebrewers. Boring purist that I am, I was hesitant to request any samples at first, happy to stick with the reliable single strains I’ve come to appreciate. Then as news of this so called Frankenyeast blend began to spread, Dan Paris from the In Bounds Brewing blog suggested this might be an ideal yeast to use for yet another fermentation temperature xBmt, explaining a warmer fermentation ought to encourage the expression of esters from the plethora of English strains in the mix while a cooler fermentation should favor the less expressive yeasts.

Given the unexpectedly interesting results from the prior xBmts on this variable, I agreed with Dan that the Frankenyeast blend provided a rare opportunity to test a unique facet of fermentation temperature and put in my request for a couple samples.

| PURPOSE |

To evaluate the differences between 2 beers of the same recipe split into separate fermentors and fermented with the same “Frankenyeast” yeast blend where was half fermented cool (60˚F/15.5˚C) and the other half fermented warm (73˚F/22.8˚C).

| METHODS |

For this xBmt, I went with a play on my Tiny Bottom Pale Ale recipe using different hops, mostly because I hadn’t had an easy drinking Pale Ale on tap for awhile.

Frankenyeast Pale Ale

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 11 gal 60 min 42.5 IBUs 8.1 SRM 1.050 1.008 5.6 % Actuals 1.05 1.004 6.0 % Fermentables Name Amount % Pale Malt, 2 row (Gambrinus) 16.5 lbs 73.13 Vienna Malt 2.812 lbs 12.47 Caramel/Crystal Malt - 15L 1.5 lbs 6.65 Victory Malt 1 lbs 4.43 Caramel/Crystal Malt - 60L 12 oz 3.32 Hops Name Amount Time Use Form Alpha % Columbus (Tomahawk) 21 g 60 min First Wort Pellet 14.1 Amarillo 28 g 25 min Boil Pellet 8.9 Amarillo 28 g 10 min Boil Pellet 8.9 Cascade Hops 21 g 10 min Boil Pellet 6.1 Cascade, New Zealand 70 g 2 min Boil Pellet 6.1 Amarillo 28 g 2 min Boil Pellet 8.2 Yeast Name Lab Attenuation Temperature Frankenyeast Frank 77% 65°F - 70°F

Two days before brewing, I pitched both vials of Frankenyeast into a single yeast starter in order to ensure equality between both batches.

Since this was a rare afternoon brew day, I weighed out and milled the grain while my strike water was coming to temp.

After transferring the slightly overheated strike water to my MLT for pre-heating, I mashed in to hit a slightly lower than planned mash temperature. Meh.

Since this batch would be split post-boil, I brewed a standard 10 gallon batch using the mash in a bag (MIAB) batch sparge method. After a 60 minute rest, I collected the first runnings then added the sparge water, which I ran off to collect the proper pre-boil volume of sweet wort.

With the flame on full blast under my full kettle, the was boiling vigorously within about 15 minutes.

Hops were added over the hourlong boil, after which I quickly chilled the wort to a few degrees above my groundwater temperature, which is fairly warm this time of year.

The chilled wort was equally split between two 6 gallon PET carboys then one was placed in a chamber controlled to 60˚F/15.5˚C and the other was placed in a chamber controlled to 73˚F/22.8˚C. While the warm ferment batch was ready to pitch after about an hour, I waited until the cool ferment wort had reached its target fermentation temperature before splitting the yeast starter between the carboys. Twelve hours later, differences were easily noticeable.

After another day, the cool ferment beer was finally starting to show signs of activity, its appearance quite a bit different than its warm ferment counterpart.

It took another 12 hours or so for a full kräusen to develop on the cool ferment batch, and as expected, it required more time to finish fermenting. After 6 days, the warm ferment beer looked to be done while the cool ferment beer was still chugging along.

The kräusen on the cool ferment batch finally drop 11 days after the yeast was pitched, and indication fermentation was nearing completion, so I took preliminary hydrometer measurements that showed both beers were at the same SG.

I left the beers alone at their fermentation temperatures while I attended a family event away from home, taking second hydrometer measurements when I returned that confirmed both had indeed reached FG. It was at this point I cold crashed, fined with gelatin, and kegged the beers.

The full kegs were placed in my full chamber and hit with 40 psi of CO2 for about 24 hours before being dropped to serving pressure. When it came time to collect data the following weekend, the beers were carbonated, clear, and ready to present to tasters!

| RESULTS |

A total of 21 people participated in this xBmt, each blindly served 1 sample of the cool ferment beer and 2 samples of the warm ferment beer. While 12 tasters (p<0.05) would have had to accurately identified the unique sample in order to reach statistical significance, only 10 (p=0.12) were able to do so, suggesting the participants in this xBmt were not able to reliably distinguish a beer fermented with the Frankenyeast blend at 60˚F/15.5˚C from the same beer fermented at 73˚F/22.8˚C.

Given the variable of investigation, I thought it’d be interesting to share some of the blind comparative evaluation data, though it should be interpreted with caution since this xBmt failed to reach significance. Of the 10 people who correctly chose the cool fermented beer as being unique in the triangle test, 5 said they preferred it over the warm ferment sample, 3 reported preferring the warm ferment beer, 1 had no preference despite noticing a difference, and 1 person felt there was no difference between the beers. Furthermore, in conversations following completion of survey and revelation of the variable, many of the participants incorrectly believed the warm ferment beer to be the one that was fermented cool.

My Impressions: I made 6 triangle test attempts served to me by different people at different times with the unique beer being picked by the server. I was correct twice, which is exactly chance, and exactly opposite of what I thought would be the case. Similar to Jake’s experience with Frankenyeast, both of these beers were super clean with very little of the esters I expected given the plethora of English yeast strains included in the blend. Crisp and refreshing with an odd though not off-putting character I can’t really describe, neither of these beers were perfect, but both were definitely drinkable. I didn’t pull any yeast off for future use, which I’m not distraught about.

| DISCUSSION |

Two of the yeasts in the Frankenyeast blend were WLP036 Dusseldorf Alt and WLP080 Cream Ale Blend, the former a hybrid strain that works well at cooler temperatures and the latter a blend that includes an actual lager (s. pastorianus) strain. While 60˚F/15.5˚C is certainly warmer than traditional lager fermentation temperatures, I fully expected these yeasts to express themselves more in the cool ferment beer, while I was convinced the warm ferment beer would have been an ester bomb, especially since 73˚F/22.8˚C is quite a bit warmer than most would ferment with anything other than a Saison strain. The fact they were so similar has yet again shaken my conviction that fermentation temperature is one of the most important components of brewing good beer.

These beers should have been different!

I honestly don’t get how a 13˚F/7˚C spread using a yeast blend with strains known for their ester production didn’t produce beers so vastly disparate in character that every participant could distinguish them. I couldn’t even tell them apart and I brewed the damn beers! One plausible explanation that I’ve discussed with others following every other xBmt focused on this variable is that temperature alone may not be the important factor, but rather precise control of fermentation temperature, with some speculating temperature variance is what causes problems. This is definitely something we’ll be getting to at some point soon. Until then, I’ll remain stumped and confused.

If you have thoughts about this xBmt, or if you happened to be one of the few people who got some Frankenyeast, please share in the comments section below!

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