Have you heard about using olive oil in beer fermentation instead of oxygen? As homebrewers, we are always looking for ways to improve our beer. If something as simple as adding a minute amount of olive oil to the starter or wort prior to fermentation can increase the ester production and flavor stability, then in theory, I'm all for it.
As we all know, oxygen can only be added at the beginning of fermentation and that we take great care to exclude it after fermentation is underway. The reasons are fairly obvious. Oxygen causes oxidation reactions which ultimately results in staling of the beer or reduced flavor stability. Oxygen is necessary for the yeast to reproduce. They use oxygen to synthesize sterols and unsaturated fatty acids for its cell walls. Boiling the wort is necessary for isomerization of alpha acids in the hops. But, boiling also drives off all the oxygen in the wort. For this reason, oxygen is always added to a wort prior to pitching yeast as it has always been considered to be essential to yeast growth. It can be added by shaking, stirring vigorously, splashing during transfer, aeration with an aquarium pump, or oxygenation with pure oxygen.
Many homebrewers store yeast from previous fermentations and reuse them several times. These yeast have been through a lot and are typically deficient in sterols and unsaturated fatty acids. Oxygenation of the wort is necessary to get these yeasts healthy so the fermentation can progress without any problems and off flavors being produced.
So we know why oxygen is necessary, but what are the downsides of oxygenation? There is a narrow window of when you can oxygenate the wort prior to fermentation. We can't oxygenate the wort until it is below 80°F (27°C) due to hot-side-aeration (HSA) which significantly reduces the aging potential of your beer. Oxygen additions after the yeast have finished the lag phase just leaves extra oxygen available for oxidation reactions. It is difficult to know exactly how much oxygen you are adding. You can only get to 8 ppm (saturation level) by shaking, splashing, or aerating with an aquarium pump. Wyeast Laboratories say that "it is generally safe to assume that you need at least 10 ppm of oxygen...10 ppm will supply adequate oxygen in most situations." Over-oxygenation is not usually a problem, but extreme cases can lead to off flavors. Inadequate levels of oxygen are usually the problem for most homebrewers. This can lead to poor yeast growth which in turn leads to poor attenuation, long fermentations, off flavors and aromas, and problems in the yeast which may make them inadequate for reuse.
So what if we could do away with the headache of deciding how much oxygen to add, when to add it, and what is the best way to add it. Wouldn't that simplify our lives as homebrewers? Not to mention the added benefit of improved aging and flavor stability.
One method which has gotten a lot of press lately and been circulating throughout the various forums is the addition of a miniscule amount of olive oil in beer yeast instead of oxygen. The idea goes like this. Yeast need oxygen to produce sterols and unsaturated fatty acids (UFA) for their cell walls. If we supply the UFAs to the yeast, then they won't need oxygen.
Olive oil is a very complex compound made up of many components. These include acids, vitamins, volatile components, and water soluble components. The three primary fatty acids (or triglycerides) are oleic acid (55-85%), linoleic acid (3.5-21%), and linolenic acid (0.0-1.5%). Oleic acid is the most abundant fatty acid found in nature. It is the oleic acid that studies have shown can reduce blood levels of total and LDL (bad) cholesterol. In our case, it is the oleic acid that supplies the UFAs necessary for yeast growth and proper fermentation.
It has also been proven that by adding UFAs (in the form of olive oil) to wort can increase ester production. It was found that the beers fermented with olive oil had increased ester content, although the increase was not out of specs for the beers produced (in the New Belgium brewery where the tests were conducted). Other results were that fermentations were a little slower but they did finish at the same gravities as those that were oxygenated instead. Perhaps the best result for big breweries and us as homebrewers, was that normal fermentations can be achieved with improved flavor stability.
So how much olive oil in beer yeast should I be using? During the trials, New Belgium brewery would pitch 4500 liters of yeast into 168000 liters of beer. Into the 4500 liters of yeast, they would add 300 ml of oil. To scale this down for 5 gallons, we need to use about 0.0000833 ml of oil. For almost everyone, this is impossible to measure. There are 60 drops of olive oil in a teaspoon, and a teaspoon is 5 ml, so a drop is about 0.0833 ml. You would need about 0.001 or 1/1000 of a drop. As you can see, the amounts are miniscule. It was suggested on Northern Brewer's forum that one way to get this small amount would be to dip a toothpick into the olive oil and then transfer this amount over to the wort. Sounds good to me, and I believe many homebrewers are using this method to get the right amount in their wort.
So, for the adventurous homebrewers out there, try it. I believe it has been documented and experimented enough by everyone to be safe and reliable means of increasing both the flavor stability and ester production in your beers. The next question to be answered is how will olive oil in beer it work in lagers, where we don't want any ester production?
References: Information for this article on Olive Oil in Beer was taken from the paper Olive Oil Addition to Yeast as an Alternative to Wort Aeration Grady Hull-New Belgium Brewing Company, Fort Collins, CO USA 9/26/05, the paper entitled FLAVOURS IN BEER BY ROGER A. MUSSCHE AND FLORIS R. MUSSCHE, the sales brochure for theOxygenation page from the technical information section of Wyeast Laboratories website, and the thread by many homebrewers in Northern Brewers forum.
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