Originally Posted by agenthucky
" Moreover, olive oil will not dissolve in wort and must first be dissolved in 100% ethanol. For any homebrewers reading this – do not add a drop of olive oil to your beer. I had to weigh 1 gram of oil, dissolve it, and make a serial dilution until I had close to 0.1 ug/ml. Of this solution, I added 100 uls directly to the wort."
Has anyone else come across this? This is the first I've seen of this and no one else is talking about this. Where does this come from? The solubility of oil in water? This seems like an important part of testing this theory and I haven't seen it anywhere.
You can think of it this way. Imagine the olive oil is corn starch and the wort is hot soup. Maybe you've encountered this during cooking: if you plop a tablespoon of corn starch in the soup, you are going to get a ball of cornstarch floating in soup. If you break it up it will still be dry in the center. That's because the corn starch repels the water enough that it can't wet the inside.
Now, if you swirl the corn starch in cold water until it is suspended before adding it to the hot soup, the starch will dissolve into the soup and work as intended.
The olive oil works the same way. Added to water it remains a 'blob' like the corn starch, with most of the oil unavailable to the solution. Even if it breaks up into tiny bubbles, these are still huge compared to the yeast and the liquid between these bubbles contains zero molecules of oil. Since the olive oil is essentially being used as a vitamin to replace a product of yeast's aerobic metabolism, this is not ideal.
However, if you dissolve the oil in ethanol, it is like suspending the corn starch, only even more so. When dissolved, all molecules are separate and enter the wort separately. They spread throughout the wort and are much more available to the yeast. Over time they might reassemble, but it would take a very, very long time and hopefully the yeasties would chomp them up before then.
I looked up some studies using my academic access. Under fairly aerobic (i.e. healthy) conditions, it looks like Sac make close to 3.5mg/kg palmitoleic acid, dry cell weight. Palmitoleic acid would be the limiting constituent in just about any plant oil you could add, so we'll take it as a basis. I haven't dehydrated and weighed my yeast after a fermentation, but if someone were to do so it would be easy to find out the right amount of oil to add:
(weight of cake)* (3.5mg/kg) / (0.3-3.5% palmitoleic acid in olive oil)
or, since the numbers work out so nicely,
1-10mg/100g of anticipated dry yeast cake per batch
Taking a conservative guess at 100g of dry yeast cake for a 5 gallon batch, I get 10mg (or 0.011mL) of olive oil per 5 gallon batch (in line with other estimates), or appx 1.1mL of a 1% v/v olive oil solution in ethanol
I don't know if its been mentioned earlier in the thread, but extra virgin olive oil is not the best choice. You want the thinnest, yellowest, most tasteless olive oil you can find to reduce phenolic content and ester generation. Macadamia oil might be a better choice because of its lower phenolic content (~48mg/kg vs 220mg/kg for the lightest olive oil)* and higher concentration of palmitoleic acid, which yeast need the most. What flavor is there is nutty rather than fruity or bitter, which should blend into the malt profile much nicer, although it would take a prince's nose to detect any flavor in 5 gallons: you'd be adding only 0.22mL of a 1% solution of macadamia oil in ethanol to match the above calculations.
Forgive me if any of this was explored earlier in the thread as I only heard of the idea today, and haven't yet read the whole thing.
*Influence of Oxygen Addition during Growth Phase on the Biosynthesis of Lipids in Saccharomyces cerevisiae (M330-9) in Enological Fermentations, Valero et al.
*Antioxidant properties of phenolic compounds in macadamia nuts, Quinn & Tang