Olive Oil vs. No Aeration

drew's picture

In September 2005, Grady Hull of New Belgium, developed a new technique of strengthening yeast in storage by adding olive oil. The theory was that yeast use oxygen to synthesize sterols to build stronger, better cell walls so instead of introducing beer staling oxygen to the mix - why not add a tiny drop of cheap olive oil, a source of sterols, directly and let the yeast do it's thing. Cheap olive oil vs. expensive aeration equipment

Many homebrewers just read the "cheap" part and didn't read the rest of his study. Instead they rushed out to add pin drops of oil to their fermenters and rejoiced at not having to run oxygen anymore! First and foremost - while his study found increased stability from the yeast treated this way - it never studied the addition of oil to the fermenter - just the storage tanks where it was dispersed evenly in an alcoholic solution. This is a big difference in the amount of time the oil has to be absorbed/used and the number of cells exposed. In contrast the usual homebrew method of adding a drop to the carboy and shaking it before pitching doesn't appear to adequately disperse the oil or give the yeast enough time to absorb it before hitting the fermentation slopes!


Proposed By: 


Does the addition of olive oil to a fermenter replicate the organoleptic impact of aeration on a the beer versus doing no aeration at all?


The olive oil batch will not be qualitatively different to the no aeration batch

Brewing Sessions Needed: 



Special Equipment/Process: 

Add the olive oil to the fermenter before adding the wort. Use vodka to completely dissolve the oil in the sample jar.

Experimental Procedure: 

  1. Create equal sized starters of yeast (or start with equally viable packets of yeast) - The same strain
  2. Brew enough Simplified Amber to split evenly between two fermenters (e.g. brew 5 gallons and split evenly into 2.5 gallons for fermentation). Record the Original Gravity.
  3. Prior to adding the wort to the fermenter, add 50 uL of olive oil. Use a small amount of vodka to dissolve the oil from the sample container. Pitch the yeast.
  4. For the second vessel, simply transfer the cooled wort and pitch the yeast with no oil/aeration/swirling.
  5. Ferment both batches in the same space and under the same conditions, especially temperature. Match the fermenters and other equpment.
  6. After fermentation subsides, record the length of fermentation and the final gravities.
  7. Package the two beers in exactly the same fashion. (Bottle primed with sugar, kegs and force carbonated, etc) - Record packaging methodology
  8. Perform a triangle test and record the results
  9. Ask the testers for their observations on the samples. DO NOT Reveal the Difference between the samples
  10. Discuss the results and record any further observations

Recipe Link: http://www.experimentalbrew.com/recipes/simplified-amber

"Cap the carboy/bucket and

"Cap the carboy/bucket and swirl the vessel to stir the oil into the wort. "

This might introduce some aeration - shouldn't the other batch also be similarly swirled to control for that? Alternatively, the olive oil could be added to the bottom of one fermentor before adding the wort to them to ensure distribution and equivalent levels of aeration (minimal).


twitter: @allawayr for some beer but primarily science thoughts

Should the fermenter be

Should the fermenter be purged with CO2 to minimize aeration? Then you could swirl it.

I think using dried yeast

I think using dried yeast would be a problem because the manufacturer claims dried yeast don't need aeration.

Does the type of olive oil matter?

You should have split it

You should have split it three ways with one batch receiving aeration. Me thinks you wouldn't be able to tell difference between all three.


drew's picture
Much harder to do a test with

Much harder to do a test with that sort of split. I think the main point will be - is it true, my assertion, that OO vs. no aeration doesn't make a difference.