I don't think that food in cans should be contaminated while it is being opened, maybe there should be a canning skill, and lower it is, the higher is the chance of contaminating food? It still would be very low (if the poisoning effect would be strong). Using fuel in a dungeon cannery is a good idea, because we seal cans by putting them in boiling water irl, so... I guess it is realistic. And, if there is a wand of sealing, maybe there should be a wand of unsealing, that could be used to trigger mines, open doors, ribcages, chests, walls, etc. Also, if we are adding canning, then we have to add pickles.
EDIT: Canning is actually easy, all you need is a jar (or a can), a source of heat, a large pot, and a sealing tool. So we could add campfires to the crafting system (if it isn't there, idk), adapt cauldrons/add pots and add a sealing tool and that would be it. Do we really need to build up a lot around the concept of canning? Probably not.
P.S. Praise Pickles