So I recently got a propane burner to brew outside (it's way too hot to be brewing inside), and I noticed something weird. As the wort came to a boil, it seemed like there was some oil floating on top. Before, on the stove top, I had never seen this. Note, this was before any addition of hops, this was pure grain wort. Any idea what this was?
Perhaps when boiling on the stove top, the boil took so long that these oils were emulsified before the boil (longer at high temps), as opposed to a quicker boil that didn't emulsify the oils before the rolling boil took hold?