Author: Jason Cipriani

Yeast pitch rate is viewed by most brewers as being one of the more important components to crafting good beer, with inadequate amounts contributing to under-attenuation and certain undesirable off-flavors. According to many, pitching the proper amount of yeast can lead to quicker starts to fermentation, faster finishes with complete attenuation, improved consistency and predictability, and generally higher quality beer.

Countering these claims are the results of numerous xBmts we’ve performed on pitch rate. Tasters have been largely unable to distinguish beers pitched with recommended cell counts from those pitched with either too little or too much yeast. Not unexpectedly, comments from readers following publication of these results have tended to offer possible explanations as to why the difference wasn’t greater, a common one of which had to do with the yeast strains being used.

Belgian Ales are known for possessing unique characteristics such as spicy phenols and fruity esters, which particular yeast strains are known to contribute. Compared to more notably cleaner yeasts, it’s believed that those used to make Belgian Ales are more sensitive to certain fermentation conditions including pitch rate– pitching too little yeast can result in over the top spiciness to the point of being unpleasant, while pitching too much can lead to an out-of-style ester bomb. I decided to test this claim out for myself with a Belgian Dark Strong Ale.

| PURPOSE |

To evaluate the differences between a high OG beer fermented with either a yeast starter or direct pitch of the same Belgian Ale yeast.

| METHODS |

For this xBmt, I went with a slightly modified version of Ray Found’s Belgian Quad recipe, a style I don’t brew often and was excited to have on tap.

Bain de Sang

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.5 gal 90 min 42.6 IBUs 24.7 SRM 1.084 1.014 9.4 % Actuals 1.084 1.008 10.2 % Fermentables Name Amount % EuroPils (Cargill) 15.75 lbs 82.89 Special B Malt 4 oz 1.32 Candi Syrup, D-180 1 lbs 5.26 Candi Syrup, D-90 1 lbs 5.26 Cane (Beet) Sugar 1 lbs 5.26 Hops Name Amount Time Use Form Alpha % Columbus/Tomahawk/Zeus (CTZ) 28 g 60 min Boil Pellet 13 Willamette 28 g 15 min Boil Pellet 5 Yeast Name Lab Attenuation Temperature Monastic (B63) Imperial Yeast 76% 68°F - 78°F Notes Water Profile: Ca 15 | Mg 2 | Na 0 | SO4 22 | Cl 16 Download Download this recipe's BeerXML file

Relying on my favorite pitch rate calculator, I threw together a starter of Imperial Yeast B63 Monastic, the size of which was based on manufacture date. At the time of yeast pitch, the single pouch of yeast was estimated to have approximately 100 billion cells remaining, as it had been manufactured nearly 2 months prior, whereas the yeast starter was estimated to have closer to 400 billion cells.

On brew day, I started off by turning the flame on under my keggle of brewing liquor, which I’d treated to achieve my desired profile. While the water was heating, I weighed out and milled the grain for a 10 gallon batch.

With my water at strike temperature, I stirred the grains in before checking the mash temperature.

I began recirculating the wort and set a time for 60 minutes, stealing a small sample to check the mash pH about 15 minutes in.

At the end of the mash rest, I batch sparged with water I’d preheated with my HotRod heat stick. Once the pre-boil volume of wort was in my kettle, I hit the flame and moved on to measuring out the kettle hop addtions.

In addition to hops, various sugars were added during the boil at the times stated in the recipe.

At the completion of the boil, I ran the wort through my plate chiller directly into separate sanitized fermentation vessels, each receiving an identical volume.

At this point, I took a hydrometer measurement that revealed the wort was at a respectable 1.084 OG.

The filled fermentors were placed next to each other in my chamber to finish chilling to my desired fermentation of 72°F/22°C, which the crew settled on given the particular yeast strain and beer style. After a couple hours, I returned and pitched the starter into one batch while the other was direct pitched with a pouch of the same yeast.

The batch pitched with the yeast starter was active the following day and going crazy at the 48 hour mark, a point at which the direct pitch beer had yet to show any sings of fermentation. My nerves settled the next, approximately 60 hours after pitching the yeast, when I noticed airlock activity on the direct pitch batch. After 11 days, I noticed signs of fermentation were absent, so I took hydrometer measurements that showed a very slight difference in attenuation between the beers.

I proceeded with kegging the beers.

The filled kegs were cold crashed in my keezer, fined with gelatin, and burst carbonated. I let the beers condition for 2 weeks while I was on a business trip before serving them to blind participants.

| RESULTS |

A total of 20 people of varying levels of experience participated in this xBmt. Each participant was served 2 samples of the standard pitch rate beer and 1 sample of the direct pitch beer in different colored opaque cups then asked to identify the unique sample. At this sample size, 11 tasters (p<0.05) would have had to identify the unique sample in order to reach statistical significance, though only 8 (p=0.34) made the accurate selection, indicating participants in this xBmt were unable to reliably distinguish a Belgian Dark Strong pitched with the recommended amount of yeast from one that was pitched directly with a single pouch of yeast.

My Impressions: When tasting these beers side by side, I was confident there was a difference. I perceived the direct pitch beer as having a slightly thinner mouthfeel than the standard pitch rate beer. Then I completed a total of 7 semi-blind triangle tests and picked the odd-beer-out only once. Despite my beliefs, these beers were the same when I wasn’t aware of which one I was drinking. The beer was actually very good! My wife best described it as having a “spicy banana” flavor, though it’s not all spice, I think it is nicely balanced with a nice malt character and a hint of raisin in the finish.

| DISCUSSION |

“Adequate” is relative when it comes to pitch rate, as certain styles demand varying amounts of viable yeast to produce the intended outcome. Most modern brewers agree that under-pitching yeast is rarely ever ideal, as it increases yeast stress such that certain undesirable off-flavors can be produced. However, a slight under-pitch is used by some as a technique to add character to certain styles of beer that would otherwise be absent given a higher pitch rate.

It’s commonly claimed that the stress put on Belgian yeast from being under-pitched can lead to increased levels of phenol and ester production, which can be highly desired for these types of beers. For this reason, some brewers ignore typical pitch rate recommendations when making these styles, choosing instead to pitch a bit less than purportedly optimal rates. However, tasters in this xBmt were unable to reliably distinguish a Belgian Dark Strong Ale pitched with an adequately sized starter from one that was direct pitched with a single pouch of yeast.

With a number of past xBmts on pitch rate returning similarly non-significant results, it would seems the evidence is pointing to propagation of yeast in starters as being less necessary than many believe. I’ll admit, as a proper pitch rate proponent, I fully expected the beers in this xBmt to be different, and the fact they weren’t has left me somewhat conflicted.

It seems plausible that yeast quality is playing a role here, as labs like Imperial Yeast are producing a high quality product that may simply maintain viability longer than the yeast of 10+ years ago. Or maybe our understanding of pitch rate, and the beliefs we hold about its importance, is incomplete, even when it comes to more characterful strains like like those used to ferment Belgian ales. Either way, while I’ll likely continue building starters for most of the beers I brew, I won’t fret about direct pitching if I have a free afternoon and decide to brew.

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

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