This is a sign of food guarding. Therefore to stop it, you need to stop food aggression as a whole. Which will require patience, and gradual positive reinforcement. The key is to never punish your dog for growling. They are not doing so to anger or disobey you, there is a cause and that needs to be figured out. As your dog becomes more comfortable with you interacting with their food and being around them eating, they will stop growling.