You need CO and NO gases to make smoke rings because those gases combine with myowater in the muscle cells. One without the other doesn't make the rings. Very hot charcoal makes the most gases (of things one would use to smoke meat), propane makes hardly any; Electric makes hardly any.
I am not surprised that I don't get any smoke ring in my meats on the electric smoker, even with pellets and wood chips.
- Torg