Stop villagers from making bread

Solution 1:

Villagers who pick up wheat, won't share it with other villagers. They will instead bake bread and share 50% of the bread they have (if it's in large quantities) with others who need food. As far as I am informed making a wheat farm is impossible if you want to use villagers, due to the reason mentioned above.

You can, however, make potato or carrot farms with farmer villagers (the ones with brown coats and no other collars), but make sure they have an empty inventory - when new villagers are born after mating they have empty inventory until someone throws something at them. If your villager is planting stuff you don't want him to just walk around with him and destroy his seeds, you will then pick them up and he is gonna use up all of his supplies for planting.

After that, you can throw him the types of seeds you need him to plant for the farm. Keep in mind that farmers won't pickup or plant sugarcanes.

My advice would be, if you need the bread for your own consumption, to just instead make a potato farm.