Food refusal education
Place the food in several plain locations, then guide the dog toward it as he gets closer to it. As soon as he shows signs of hunger, firmly command "no" and pull the leash to stop. If he stops picking up food, you should encourage him by petting him. Then repeat the process by taking him to another location with food.
Additionally, you can spread out some of the food in a more secluded/isolated area. Change to a training leash, you can be far away from the dog and still use the training method described above, until there is no longer a need for a leash and the dog responds to commands while moving freely without picking up food. You should frequently pair it with mechanical stimulation to strengthen it so as to prevent the dog's conditioned reflex from waning or eventually disappear.
To train your dog, you can also use some meat pieces that have been marinated in chili oil or flavored with chili peppers. To help your dog to remember, you will lead him to eat chili meat pieces while he tastes the flavor.
Pour the broth over the chili meat completely so that it covers the chili flavor. Otherwise, the dog will not fall for the smell of chili.
If the dog is able to refuse food from a stranger while the owner is present, then additional training in food refusal can be given. Then you ask a friend to feed your dog while you remain hidden so that the dog cannot see you. Say "No!" and stop him if he tries to eat.