How old is the dog?
To me that would make a great deal of difference in how you would go about instilling in the dog that he/she cannot and doesn't have any need to guard/protect their food or any other object. With a younger dog just take it from him, and then hold it a second or two and give it right back to him with much praise (as long as he didn't react negatively.
BTW, a lot of the times, with many dogs (don't know about yours, of course) the WAY that you take it and your body language can make a HUGE difference in the dog's reaction. Just walk right over to many dogs like you KNEW that you could and you expect no nonsense, and the dog will just stand there and let you. However, go to him like you expect a problem i.e. hesitantly or the like and the dog is MUCH more apt to think that he can get away with "protecting" his stuff! Of course you also have to have Plan B if he does react to you taking it.
Obviously, if you are afraid of your dog or just are reluctant to have any type of confrontation - then don't. Get a trainer/behaviorist to be right there to assist you.
We saw a similar thing with my dog (now a 4+yo male bossy GSD), only it was to do with getting a collar and leash on him in his run. I was laid up with a knee replacement and we hired a dog walker - first few times went fine and then one day he just decided he didn't have to get his collar on, so he reacted when the walker tried to put it on him. I think that the walker was always a little bit afraid/cautious with our guy and she finally admitted one day that she couldn't get his collar on for one day. A second person had no problem with him at all - we think it was due to the approach of the two different walkers - one was a little hesitant and it showed while the other wasn't at all. Our dog never gave the second one any problem at all. Now our dog was an adult about 2yo when this happened and had been called "very dominant and a bully" by his breeder, and he just tried to get away with his own way. BTW, When he was younger, he tried a couple times with me not to do something i told him but hasn't tried anything for a long time now.
He has to learn that you, or any other family member, can take anything he has away from him for any reason or for no reason. Not that you will do it a lot, but he has to learn that you can w/o ANY negative reaction from him, much less growling or snapping.
Good luck with your pup.