You might also want to see if you can get him trained NOT to eat anything...even his own food...UNTIL he is given a command from you. I train mine with "all yours" as the command. Also, if he already knows to "leave it" on command, maybe you can use it to stop him until you have a chance to see if it is something he can have regardless where it is...even if you also use a muzzle.
The "all yours" command is something I am working on training to Brody and Mia because I see both of them 'grazing' in the yard and I do not trust what people fling out of their car windows.
Training for "all yours" is also a "people" command since everyone who will handle the dog must remember to give the "all yours" command when food is given during normal feedings. It gets easier to remember to give your dog the command after about the first month, but if the dog learns before you do, you may find your hungry dog antsy dancing around you, etc.!
Plus, we also have cats, and there, are other wild critters in the woods nearby, and who knows what might get dragged home or fall off a garbags truck, etc., and Brody has twice now eaten some kind of ick from the yard which he proceeds to hurl within a few minutes, but I completely understand your concerns and reasoning. Their mouths are only inches if that above their next disgusting or dangerous 'snack'.