My boy snapped at me once when he was finding his place in the pack so i booted his food bowl away and shouted loud "NO NO NO" all the wile taking any space i wanted in the room. That night i ate first and he was booted out of the room and given no scraps. He was fed outside that night and when i put his bowl down i made it clear i was still not happy with a deep loud "MOVE" when he was in front of me and i was going to put it down. As i was going to place it down he got told "BACK, SIT", the bowl did not touch the ground until he did. By now he knew he was being dominated and his ears were down along with his eyes not daring to look at me. I pretended to eat some first then put it down. I waited a minutes to see if he moved, he didn't move a muscle so i said "go on then" and he started to eat. Then i made a "Ahh Ahh" put my hand right on the bowl and moved it away 3-4 times. He sat down and accepted it totally.
Never since has he ever even showed a hint of food aggression. Basically you need to let him know that is your food and if you want you'll dig it out of his gob. Eyeball him menacingly if he looks at you when you next eat. If he does put your food down, get up asserively and "OUT, OUT NOW" and lock him out the room. Always feed him after you!