Author: Jake Huolihan

A defining characteristic of Belgian beers are the phenols and esters developed by the particular yeasts used to ferment them. With a wide range of characteristics including fruit, clove, pepper and some higher alcohols, the compounds produced by these strains give the beers from Belgium the aromas and flavor loved by drinkers the world over.

Brewers have long sought to control the expression of certain compounds by way of some form of yeast manipulation on the belief that altering a specific input or process can result in vastly different outcomes. One such method has to do with the temperature at which the beer is fermented, with cooler environments purportedly favoring spicy phenols while warmer climates encourage more fruity ester development.

My consumption of Belgian beer is infrequent, but I was inspired to make one to enjoy during for the hot Colorado summer after drinking a truly great Trappist Single. With so many past xBmts suggesting fermentation temperature when using notably clean yeasts doesn’t seem to have the expected impact, I decided to test it out with a more expressive Belgian strain.

| PURPOSE |

To evaluate the differences between beers fermented with a single pack of Imperial Yeast B48 Triple Double at either 65°F/18°C or 77°F/25°C.

| METHODS |

I designed a simple recipe for this xBmt in order to allow any differences to stand out.

Frequency

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.5 gal 60 min 35.1 IBUs 4.2 SRM 1.053 1.009 5.9 % Actuals 1.053 1.007 6.1 % Fermentables Name Amount % Genie Pale Malt (Root Shoot) 5.5 lbs 47.83 Odyssey Pilsner Malt (Root Shoot) 5.5 lbs 47.83 Cane (Beet) Sugar 8 oz 4.35 Hops Name Amount Time Use Form Alpha % Perle 20 g 60 min Boil Pellet 8 Perle 20 g 30 min Boil Pellet 8 Perle 10 g 5 min Boil Pellet 8 Yeast Name Lab Attenuation Temperature Triple Double (B48) Imperial Yeast 76% 65°F - 77°F Notes Water Profile: Ca 68 | Mg 0 | Na 8 | SO4 75 | Cl 68 Download Download this recipe's BeerXML file

I collected my RO water and adjusted it to my desired profile the night before brewing.

When I woke up the next morning, I turned on the elements to heat my strike water before proceeding to mill the grains.

I then weighed out the sugar addition and kettle hops.

With the water appropriately heated, I transferred it to my MLT and let it sit for a period of pre-heating before mashing in to hit my target mash temperature.

About 15 minutes into the mash, I stole a small sample of wort for pH measurement.

When the 60 minute mash rest was complete, I lautered directly into my kettle.

The wort was then boiled for 60 minutes with hops added per the recipe.

At the completion of the boil, I quickly chilled the wort 80°F/27°C with my IC.

A refractometer reading showed the wort was sitting right at my target OG.

I let the wort sit for 10 minutes before transferring identical volumes to separate Brew Buckets.

I moved the filled fermentors to my fermentation area and attached each to my glycol chiller, one set to 65°F/18°C and the other set to 77°F/25°C. Thanks to the chilling powers of glycol, both worts were ready to pitch within 10 minutes, at which point each one received its own pouch of Imperial Yeast B48 Triple Double.

After 3 days of vigorous fermentation, I pulled samples for hydrometer measurements and found the cool ferment beer was at 1.012 SG while the warm ferment beer had already reached expected FG of 1.006. After an additional 5 days, 8 in total, signs of activity were absent so I took another set of hydrometer measurements indicating a slight difference in FG.

I then kegged the warm the beers.

The filled kegs were placed in my keezer where they were left to carbonate and cold condition for 3 weeks before being served to blind participants.

| RESULTS |

A total of 21 people of varying levels of experience participated in this xBmt. Each participant was served 1 sample of the cool ferment beer and 2 samples of the warm ferment beer in different colored opaque cups then asked to identify the unique sample. At this sample size, 12 tasters (p<0.05) would have had to identify the unique sample in order to reach statistical significance, though only 7 (p=0.58) made the accurate selection, indicating participants in this xBmt were unable to reliably distinguish a Belgian Ale fermented at 65°F/18°C from one fermented at 77°F/25°C.

My Impressions: After 3 failed triangle test attempts, all of which were complete guesses, I stopped trying and accepted the beers were essentially identical. I simply couldn’t tell them apart based on aroma, flavor, and mouthfeel. And this was fine with me because I really enjoyed the beers immensely, a delicious warm weather quaffer that, to me, had a delicate balance of spicy phenols and light citrus on top of a doughy cracker-like malt character. I thought this beer was so good that I’m reconsidering my stance that pale lagers are the ultimate summer beer. I absolutely plan to brew this one again!

| DISCUSSION |

After good sanitation, precisely controlling fermentation temperature is viewed by many as being the most important factor to crafting delicious beer. Moreover, when it comes to making Belgian ales, a belief held by many is that even small differences in fermentation temperature will have a noticeable impact, with cooler and warmer environments encouraging the expression of different characteristics. In curious contrast to this claim are the results from this xBmt showing tasters were unable to reliably tell apart beers fermented with a Belgian yeast at either 65°F/18°C or 77°F/25°C.

While the 12°F/7°C discrepancy in fermentation temperature may not have had a perceptible impact, there were some objectively observable differences, namely that the warm ferment beer finished fermenting quicker and 0.001 SG point lower than the cool ferment beer. Since the finished beers were, for all intents and purposes, the same, it’s possible those looking to expedite their grain-to-glass time can use warmer fermentation environments to do so without ruining their beer. At least when brewing Belgian ale with Imperial Yeast B48 Triple Double.

With so many fermentation temperature xBmts unexpectedly returning non-significant results, I’m resigned to loosen my grip a bit on the oft touted importance of precise fermentation temperature control. Given my inability to detect any differences whatsoever between the cool and warm ferment beers, along with my characteristic impatience and overall enjoyment of the beers, I’m encouraged to ferment more beers at warmer temperatures. At the same time, I have no plans to ditch my current fermentation temperature control setup, as I feel it lends a satisfying degree of control and predictability to my brewing.

If you have any thoughts about this xBmt, please do not hesitate to share in the comments section below!

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