The thought of adding oil to my beer sounds ridiculous! Grady Hull, a commercial brewer with New Belgium Brewing Co. experimented using four commercial size batches of New Belgium’s Fat Tire. Four batches were brewed adding olive oil to the yeast in storage and refraining from the usual aeration of the wort. Control batches of the same size were brewed concurrently using New Belgium’s normal wort aeration procedures. The first batches were 9,500 gallons; second 19,000 gallons and the last two were over 55,000 gallons. Most of the beer was blended prior to bottling, but a large portion of the final batch was not blended. All in all, they bottled over 1,000,000 bottles of Fat Tire that were fermented all or in part with olive oil additions.
Mr. Hull conducted these experiments for a thesis toward his MS in Brewing and Distilling from Heriot-Watt University located in Edinburgh, Scotland.
Like I mentioned earlier, it is hard to imagine adding olive oil to your beer. They compared fermentation time, yeast density, viability, alcohols produced, esters, head retention and much more. Before I mention the results of the experiments we need to cover a little theory and get some understanding of how yeast multiply and what their requirements are.
The yeast reproduce by cell division, which is also know as budding. A small yeast cell will form on the side of a yeast and when it is fully developed it will split off in a process know as binary fission. This process takes about four or five hours in your wort or starter, more or less time may be required depending on the environment and nutrients available. Yeast basically requires sugar, protein, calcium, salts, zinc and other minerals to survive. For reproduction yeast require oxygen to create the elements necessary to form the yeast cell membrane or cell wall. This process is known as synthesis.
The basis for Mr. Hull’s thesis on using olive oil was the fact that yeast uses oxygen to make or synthesize sterols and unsaturated fatty acids (UFA), which they use to grow and build the cell walls. The yeast take an atom of oxygen to remove a hydrogen to produce the unsaturated fatty acid chain the yeast need to multiply. Olive oil contains oleic acid, which is the same 18-carbon monounsaturated UFA produced by yeast. So, to put it simply, instead of providing oxygen for the yeast to produce UFA, you just provide the required UFA straight to the yeast.
At New Belgium they added different amounts of olive oil to each batch, increasing the amount toward the end. The final batches had the most olive oil added and it had the best results. Now how much olive oil did they add? They added the olive oil to the yeast that was in the holding tank about five hours before they pitched it. In the forth and final batch they added 1 mg of olive oil per 25 billion cells. If you bring that down to the size of a one or two quart starter the amount is immeasurable. For my starters I generally figure that a White Labs vile and the large Wyeast packs contain about 100 billion viable yeast cells each and a two quart starter will have about twice that many (200 billion) and 8 mg is really too small to measure.
Now for a quick look at the results for the final batch of Fat Tire brewed with olive oil. The fermentation with olive oil took about 13% longer than the control batch. Ester production was a little higher with the olive oil batch, but the test panel preferred the flavor profile to the regular batch. The big plus was the reduction in signs of oxidation in beers stored for three weeks at warm temperatures. The purpose of the experiment was to reduce oxidation and extend the shelf life of the beer, which it did.
Now you have to realize that these experiments supplied the yeast with UFA, but not the sterols the yeast also require. Mr. Hull had suggested further experiments could be conducted by adding sterols to the stored yeast or adding the olive oil in conjunction with wort aeration.
How can we apply the olive oil additions to our home brewing procedures? This has already changed my process for every starter I make and even when I rack a beer on the trub from a previous fermentation. Lets talk about putting your wort on a previous batches trub first. I have heard all the discussions about how the yeast cake that is remaining in the bottom of a carboy or fermentation bucket may have worn out, unhealthy yeast with thin fragile cell membranes. To revitalize the yeast I put a drop of olive oil in the carboy at least five hours before adding my wort. The dormant yeast will take in the UFA and build up its glycogen reserves, making them ready to rock and roll when added to the nutrient rich wort.
Now for a starter, I add a small amount to the boiling wort for my starter. My normal starters are about two or three quarts. The way I add an amount smaller that a drop is by sticking a fine wire about 1/4” into the olive oil then stirring it into the boiling wort for my starter. All of my fermentations that I have added olive oil to have been strong and clean and I have not noticed any reduction in head retention. I also add a packet of old dried yeast to the boil along with the normal yeast nutrients. I prefer the yeast nutrients that also include a little zinc. I always keep a few packets of plain baker’s yeast I purchase at the grocery store on hand to throw into the boiling starter and I also add one to my brew kettle the last ten minutes of the boil along with whirlfoc and yeast nutrients. The reason I add the dried yeast is because during reproduction the yeast will use the dead yeast cell material to make cell membranes.
Jamil Zainasheff said when he makes a starter it generally takes 18 to 24 hours to ferment out. It may take longer for a larger starter, or less time for a smaller one. If he is making a lager or stepping up a starter he will chill the started down a day or two prior to pitching. He said he generally tries to chill the yeast down to within 5 degrees F of the wort’s temperature 10 degrees maximum. Jamil then pours the beer off and just pitches the yeast.
I do not recommend forgoing aeration. John Palmer says, “Oxygen is required for sterol production, and when the sterols run out, the yeast stop budding, and this can result in a stressed or stuck fermentation. A stressed fermentation means that the yeast is not as well adapted or healthy as they should be and will therefore produce more byproducts like excessive esters and fusel alcohols. It can also mean that the yeast will be unable to take up those byproducts towards the end of fermentation resulting in high amounts of acetalaldehyde and diacetyl.” That explains the higher esters in the tests at New Belgium. If they would add the olive oil to their yeast in conjunction to normal wort aeration procedures, I bet the fermentation time will be reduced along with less ester production.
So in conclusion I think the addition of olive oil to your starter will provide extra UFA and that in conjunction with normal wort aeration will increase the yeast’s glycogen and trehalose reserves. This will help the yeast produce the sterols that were lacking in the experiment at New Belgium. The result should be a faster ferment with fewer esters produced. I am also considering adding a drop of olive oil to any beer that experiences a stuck fermentation along with a fresh pack or vial of yeast.