Author: Cade Jobe

Wort aeration, either through dosing with pure oxygen or mechanical agitation, is commonly practiced by brewers as a means of ensuring healthy fermentation. While an arguably uncomplicated process, concerns have been expressed about the contact of oxygen with wort, in large part due fears of potential beer oxidation further down the line. As such, some brewers have sought alternative means of providing yeast with the resources they need to effectively ferment beer.

In 2005, graduate student Grady Hull performed an interesting study in which he hypothesized that adding, of all things, olive oil to yeast during storage could eliminate the need for standard aeration, as the yeast would theoretically take up the unsaturated fatty acids (UFAs) needed for cell wall development. Following a series of experimental trials in which a beer fermented with yeast dosed with olive oil was compared to one aerated with oxygen, Hull concluded olive oil could be used as an alternative to wort aeration and that any objectively measurable differences in esters were small enough as to not be perceptible by tasters.

While the olive oil in Hull’s study was added to yeast harvested from a prior batch during storage, people soon began talking about additions made just prior to yeast pitch. Despite new information contradicting Hull’s conclusion, I was curious about how a beer dosed with olive at yeast pitch would compare to one that was not aerated at all and decided to test it our for myself.

| PURPOSE |

To evaluate the differences between beers fermented with and without a small amount of olive oil added at yeast pitch.

| METHODS |

My goal being to accentuate any impact of the variable, I went with my clean Kölsch recipe for this xBmt.

Livvie Lou

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.5 gal 60 min 18.0 IBUs 2.6 SRM 1.044 1.008 4.7 % Actuals 1.044 1.003 5.4 % Fermentables Name Amount % Pilsner (2 row) (Gambrinus) 8 lbs 94.12 Wheat Malt (Gambrinus) 8 oz 5.88 Hops Name Amount Time Use Form Alpha % Hallertau Magnum 10 g 60 min Boil Pellet 14 Tettnang 7 g 5 min Boil Pellet 4.5 Miscs Name Amount Time Use Type Olive Oil 8.00 ml 0 min Primary Other Yeast Name Lab Attenuation Temperature Dieter (G03) Imperial Yeast 75% 60°F - 69°F Notes Water Profile: Ca 194 | Mg 17 | Na 18 | SO4 389 | Cl 50 Download Download this recipe's BeerXML file

I started off my brew day by collecting the proper volume of water for a 10 gallon/38 liter batch, adjusting it to my desired profile, then lighting the flame under the kettle.

While waiting on the water to heat up, I weighed out and milled the grain.

When the water was ready, I stirred in the grains then checked the mash temperature.

During the mash rest, I collected out the kettle hop additions.

When the 60 minute mash was complete, I sparged to collect the target pre-boil volume.

The wort was boiled for 60 minutes then quickly chilled with my IC.

With a hydrometer measurement showing I’d hit my target 1.044 OG, I split the wort between two sanitized Brew Buckets and placed them next to each other in my fermentation chamber controlled to 54°F/12°C. At this point, I measured out 8 ml of olive oil to add to one batch, which is many times the 1 mg per 25 billion yeast cells recommended in the paper.

With the olive oil added to one batch, I pitched a single pouch of Imperial Yeast G03 Dieter into each.

The beer dosed with olive oil showed signs of fermentation activity a few hours sooner than the control batch then proceeded to ferment more vigorously (based on airlock activity) and ultimately finished 2 days before the batch fermented without olive oil. After 7 days, I raised the temperature to 68°F/20°C and left the beers alone for another 4 days before taking hydrometer measurements confirming both were at the same FG.

I reduced the temperature in the chamber to 34°F/1°C for an overnight cold crash then pressure transferred each beer to separate sanitized kegs.

The filled kegs were placed in my keezer, burst carbonated, then left to condition for a week before I began serving them to participants.

| RESULTS |

A total of 21 people of varying levels of experience participated in this xBmt. Each participant was served 2 samples of the beer fermented with olive oil and 1 sample of the beer fermented without olive oil in different colored opaque cups then asked to identify the unique sample. While 11 tasters (p<0.05) would have had to accurately identify the unique sample in order to reach statistical significance, only 5 did (p=0.88), indicating participants in this xBmt were unable to reliably distinguish a Kölsch where a small amount of olive oil was added at yeast pitch in place of aeration from one fermented without olive oil or aeration.

My Impressions: Out of the 5 semi-blind triangle tests I attempted, I guessed the odd-beer-out just twice. To me, the beers looked, tasted, and smelled exactly the same– no differences esters or phenols, no signs of oxidation in either, and certainly no olive oil flavor.

| DISCUSSION |

Brewers are often willing to do some pretty peculiar things if it promises to improve the quality of their beer, for example, using olive oil in place of wort aeration. In a study comparing a beer pitched with yeast that had been stored with a small dose of olive oil to one that was aerated with oxygen, New Belgium’s Grady Hull demonstrated that, despite small measurable differences in certain compounds, people were unable to tell the beers apart. Interestingly, tasters in this xBmt were similarly unable to distinguish a beer dosed with olive oil at yeast pitch from one that received no aeration at all.

While the results of this xBmt showed that tasters we unable to perceive differences between the beers, the fact the one with olive oil added at yeast pitch not only had reduced lag but fermented with more vigor and finished earlier suggests the method may have had an impact. Whether this is enough to justify adding olive oil to one’s beer is up to each individual brewer to decide.

Prior to this xBmt, I presumed olive oil would have no impact on beer and was surprised with the observed difference in fermentation activity. However, since both beers tasted exactly the same to me, corroborating the xBmt results, I won’t be using olive oil in place of aeration in the future.

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

Support Brülosophy In Style!

All designs are available in various colors and sizes on Amazon!

Follow Brülosophy on:

If you enjoy this stuff and feel compelled to support Brulosophy.com, please check out the Support page for details on how you can very easily do so. Thanks!

Advertisements

Share this: Facebook

Twitter

Pinterest

Tumblr

Email



Like this: Like Loading...