This is a tough problem. Firstly, looking for ways to deny him food will not work. While you spend 10 minutes to think of how to deny him the food, he spends his entire waking hours watching you, scheming how to get his paws on your plate.
There is a series of actions to take to discipline a cat. Cats, unlike dogs, cannot anticipate your thoughts and they usually fail to make connection between their actions and the discipline. Therefore, you have to discipline him only when he is on action, i.e., you have to ambush him.
Here are some suggestions when you catch him red pawed:
- Blow air to his face.
- Spray water to his face.
- Hit on the ground with a stick/club, like a meter or two from the animal.
- Start a vacuum cleaner near him.
- Chase him with a vacuum cleaner in your hand.
Do not do these things after the deed is done, you have to do it during the stealing process.
Another method might be beating a puppet. Take a cat puppet and put some bread in his mouth. Make sure your cat sees it. Then beat the puppet with a club or with your hands, right in front of your cat. He will probably make connections between the beating and the food stealing. You can try this a couple of times if he can't make the connection.
Keep in mind that this is kind of an extreme method, due to the intense psychological violence. I only used it to make sure that my freely wandering cat doesn't walk on the kitchen counter.