The release can be taught with or without food. In this video I use food.
If you want to teach the release with food, remember that it has to be done at the stage when the puppy prefers the food over the toy. Usually when the puppy is around 8-16 weeks old. Better too early than too late. If you notice, that the puppy loses his interest to play after getting food, then you have to wait longer and try again after few weeks. Even you decided to teach the release without food, it’s good to do it before the puppy has already learned to bite hard. Otherwise the handler is forced to use stronger corrections later, which can be avoided by being precise, clear and consequent from early age.
In the beginning of this video the puppy tries to bite the toy couple of times without permission. You can see how do I correct the puppy and help her to understand what she is supposed to do after the release command. She was a quick learner like all puppies are 🙂