Well, when I was working at a Jolly Pirate Donuts in High school, I noted that the large mixer that we used to make the icing would routinely leak lubricant from the paddle shaft into the icing. Although I’m sure it was a type of food grade mineral oil, that and the metal it was lubricating encouraged me never to eat another donut.
Sooner or later, that thing likely will leak some lubricant on the food it’s preparing.
I imagine that they use all sealed bearings in those things. No lubrication is added during maintenance, the bearings just wear out and get replaced.