Hi, everyone, and thanks for the very interesting responses so far! By and large, olive oil appears to deserve at least another look.
I believe the dishwashing liquid is supposed to act as an emulsifier. How important that is remains to be seen, of course (especially given your experiences above) but the original thread on DIY defoamers suggests a small quantity might enhance its efficacy even more. That said, if I've got my multiplications and divisions right, a 5 gallon home distiller's ferment would require only about a tablespoon, using more or less the dosage you find effective. Given that the commercial silicone-based defoamer I have here specifies a slightly higher dosage (about 7.5ml. on a 5 gallon batch of wash) that should work out well. Time to experiment and report back here!
That is my understanding as well. Olive oil can provide lipids and other precursors to biomass, and in the right amounts facilitates cell growth and therefore promotes fermentation. Mineral-wise it would have to part of a more extensive formulation, but especially in high stress fermentations (i.e. a high OG) there is quite some evidence indicating that olive oil is a great "energy bar" for the yeast to snack on during work. 🙂
As far as I remember (it's been a while since I looked into that particular application) the paper I read suggested that that might be the case, but it was not exactly clear if the olive oil replace the oxygen to a certain extent, or simply made up for its lack by providing additional biomass precursors. Since the effect of both would yield similar results as far as a regular fermentation is concerned, it's difficult to tell what's what; I imagine that would require a comparative microbiological analysis of the yeast cells produced. But I digress.
Still curious about the rinsing aid liquid, though... 😀