Food, feed and pharmaceutical manufacturers are among the most tightly regulated in the world, and that oversight extends to the lubricants they use as well. Rigid laws cover the base oils allowed, the additive chemistries and treat rates that formulators can use, and how to apply the finished lubricants to equipment. A lubricant might call itself food-grade but its absolutely not food, and any foodstuff found to be contaminated with it must be destroyed and/or swiftly removed from distribution.
The U.S. Food & Drug Administration years ago designated what ingredients may be used in food-grade lubricants, under 21 CFR 178.3570, 21 CFR 182 and 21 CFR 184, so that at least is clear. And the U.S. Department of Agriculture established the main categories of lubricants used in the various stages of food production: