Does Underpitching Make More "Flavorful" Beer

drew's picture

In the never ending quest to find new ways to tinker with our beers and produce better flavors, it's been promoted that to produce more ester and phenol characters in a brew, one should pitch less yeast. 

The theory is pretty simple - esters and phenols can be by product of poor yeast health or a stressful fermentation. This gets pounded into your head during BJCP training and is one of the reasons brewers have been recommended to make starters to ensure they have plenty of healthy yeast at the ready to tackle the job.

Since the goal of many beer styles is focused on cleanliness and presentation of hop/malt/water characters in lieu of yeast characters, the advice seems sound. And it's not without tradition to support it. Many of our professional brewer friends report that they get more estery beers when they first use a new "pitchable" culture from one of the yeast companies. A number report they don't really see optimum fermentation characteristics until around pitch #3. 

But not all beer styles have the same goals. Yeast driven styles like Hefeweizen and Belgian Strongs, to name two, are heavily impacted by fermentation production. What would a Hefe be without it's characteristic clove phenol or banana/bubblegum esters. (We can debate over which is better, but I'm a clove man, myself). 

So if the theory holds true - if intentionally stressing out youu yeast strain pops more aromatic compounds from the additional work - then we should be doing this with our yeast heavy styles. (There are tradeoffs as well such as fermentation health and completion, but we'll assume we're starting with vital yeast to begin with)

For this recipe, we're giving ourselves a leg up on the stress by using a Belgian Strong Ale. (Why no Hefe? Well, we have plans for Hefe). So here we start with the ideal situation - big beer, a yeast that produces character, etc. Let's do this shall we?

Experiment Status: 


Proposed By: 



Does intentionally underpitching a beer cause a change in perceived esters/phenols?


There will be a noticeable difference between the sample beers due to higher levels of aromatic compounds in the underpitched beer

Brewing Sessions Needed: 



Special Equipment/Process: 

To even things out and give our testers the best shot at reducing error - we'll be using fresh packs of yeast for this experiment. Otherwise, this is a straight pitch and ferment experiment.


Special Observations: 

  • Note the aroma/flavor compound differences between the two beers.
  • Does the underpitched beer really smell radically different?
  • Are the aromatic compounds higher in the underpitched beer?

Experimental Procedure: 

  1. The night before the brew day, smack and activate the yeast packs
  2. Brew enough volume of the Abbot's Vacation recipe to split the wort into two equal fermenters. Chill and prep the wort/fermenters exactly the same. For this experiment, please note your aeration technique
  3. To one volume, pitch one pack of yeast. To the second portion pitch two packs.
  4. Ferment both batches in the same space and under the same conditions, especially temperature. Match the fermenters and other equipment.
  5. After fermentation subsides, record the length of fermentation and the final gravities.
  6. Package the two beers in exactly the same fashion. (Bottle primed with sugar, kegs and force carbonated, etc) - Record packaging methodology.
  7. Perform a triangle test and record the results. Record the perceived aromatics of the samples.
  8. Ask the testers for their observations on the samples. DO NOT Reveal the Difference between the samples.
  9. Discuss the results and record any further observations.

Experimenters Questions: 

Q. What is the latest I can submit my data?

A. May 12th, 2017


Further Exploration Paths: 

How do different yeast strains react to the same treatment.
ejpejp77's picture
Should We Standardize on Pre-pitch Aeration

I usually hit my beer with 45 seconds of O2 through a stone after cooling and prior to pitching yeast.  Should I refrain from that and use only the splashing that happens during the transfer from kettle to fermenter?  Shake for a few minutes?  Do we care?

drew's picture
I think the easiest thing is

I think the easiest thing is to say no aeration just to make sure everyone is on the same page. Let's see what others say.

ejpejp77's picture