This xBmt was completed by a member of The Brü Club as a part of The Brü Club xBmt Series in collaboration with Brülosophy. While members who choose to participate in this series generally take inspiration from Brülosophy, the bulk of design, writing, and editing is handled by members. Articles featured on Brulosophy.com are selected by The Brü Club leadership prior to being submitted for publication. Visit The Brü Club website for more information on this series.

Author: Richard Westmoreland

When we begin our homebrewing journey, we are told to pay attention to a few details that will either make or break our batch of beer. After sanitation, one of the top details is yeast health. We’ve all seen it on score sheets for our less-than stellar lager attempts– “Pay attention to your yeast health” and “make sure you’re pitching enough healthy yeast.”

When it comes to yeast, the term viability refers to the amount of living cells present in a population of cells. Higher viability is said to have numerous positive benefits including reduced lag, quicker overall fermentation, and decreased yeast stress that can lead to the development of off-flavors. However, pitching too few cells or too many cells, referred to as underpitching and overpitching, respectively, is also believed to lead to problems.

Lagers are traditionally fermented in cooler environments that purportedly demand higher pitch rates, as with all living organisms, yeast perform slower in the cold. Surprised by the findings of Brülosophy contributor Ray Found’s previous xBmt on lager pitch rates, I put it to the test again to see if I could replicate his results.

| PURPOSE |

To evaluate the differences between underpitching and overpitching yeast in a lager beer of the same recipe.

| METHODS |

Since my current setup doesn’t allow for 10 gallon/38 liter batch sizes, I decided to split a 5.5 gallon/21 liter batch. I brewed a California Common inspired recipe for this exBEERiment, opting to ferment it cool with a traditional lager yeast.

Uncommonly Cali

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.5 gal 60 min 46.4 IBUs 12.7 SRM 1.051 1.013 5.0 % Actuals 1.051 1.011 5.3 % Fermentables Name Amount % Pale Ale Malt 2-Row (Briess) 11 lbs 86.27 Carafoam 12 oz 5.88 Vienna Malt (Weyermann) 12 oz 5.88 Chocolate (Briess) 4 oz 1.96 Hops Name Amount Time Use Form Alpha % Northern Brewer 28 g 60 min Boil Pellet 9.9 Northern Brewer 28 g 10 min Boil Pellet 9.9 Download Download this recipe's BeerXML file

I brewed this batch on my Robobrew electric system, mashing at 152°F/67°C for 60 minutes and boiling for another 60 minutes.

After chilling the wort with my immersion chiller, I took a hydrometer measurement showing the wort was at 1.051 OG.

I then prepared the yeast by rehydrating ½ packet (~5.75 grams) of Saflager W-34/70 for the underpitch batch and and 2 ½ packets (~28.75 grams) for the overpitch batch in 95°F/35°C water.

Next, I transferred 2.25 gallons/8.5 liters of wort into two 3 gallon carboys that were placed in my fermentation chamber controlled to 50°F/10°C before the yeast was pitched. While the overpitch beer was showing signs of activity including a solid kräusen 10 hours after pitching, it took nearly 36 hours for signs to appear in the underpitch batch.

I gently raised the temperature to 62°F/17°C over the course of the next week. Once activity had halted, I took hydrometer measurements over 4 consecutive days that were all the same, indicating fermentation was complete.

Using my WiFerm Controller, I cold crashed the beers to 34°F/1°C before fining both with gelatin.

After 5 days cold, I transferred the beers to separate kegs that were placed in my keezer and burst carbonated at 30 psi for 8 hours, which turned out to be perfect! After some cold conditioning time, the beers were ready to serve.

| RESULTS |

A total of 17 people of varying levels of experience participated in this xBmt. Each participant was served 1 sample of the underpitch beer and 2 samples of the overpitch beer then asked to identify the unique sample. At this sample size, 10 tasters (p<0.05) would have had to make the accurate selection in order to reach statistical significance, though only 7 (p=0.33) did, indicating participants in this xBmt were unable to reliably distinguish an underpitched lager from one that was overpitched with the same yeast.

My Impressions: In my initial samplings, the overpitched beer seemed drier, more watery, and had a little more of a “harsh” hop bite to it while the underpitched beer seemed sweeter, maltier, and more balanced overall. However, over 4 blind triangle test attempts, I picked out the unique sample only twice, indicating any differences may not have been as strong as I thought.

| DISCUSSION |

We’ve all heard that a single pack of liquid yeast does not contain the cell count necessary for a healthy fermentation of 5 gallons/19 liters of beer, especially if it’s a few months old. While a single packet of dry yeast is said to contain more than enough cells for ale, it’s often recommended to pitch 2 or more packs into a lager to compensate for the cooler fermentation temperature. Once again, the fact tasters in this xBmt were unable to reliably tell apart a lager pitched with 50% of the recommended amount of yeast from one pitched with 250% the recommended amount calls the common advice on pitch rate into question.

Before this experiment, I’d never pitched more than a single pack of yeast into a batch, whether dry or liquid. Based on these results and my personal experience with these beers, I don’t plan to start spending more money on yeast just to match “recommended” pitch rates, as I’ve found my beers attenuate just fine and taste great to my palate doing what I’ve been doing. That said, I would like to experiment more with pitch rate on beers of higher gravity.

| About The Author |

Richard Westmoreland is a homebrewer from Houston, TX who got his start in 2015 with a 1 gallon extract kit. After his first batch, he was hooked and decided to dive headfirst into all grain brewing. Richard currently brews multiple batches per month on a Robobrew 3-in-1 electric system, and he is also the inventor of the WiFerm Temperature Controller.

Would you like to have your experiment featured on Brulosophy.com? Join The Brü Club today! The Brü Club is a growing community of curious homebrewers who regularly engage each other on topics important to us all. Membership is free and comes with all sorts of cool opportunities. Learn more at TheBruClub.com!

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