Currently all food is stackable and food cans just like melon slices, absolutely useless compared to roasted meat or ever bread.
Suggestion is:
(FoodValue of itemstack[0] / 20) + 1 == amount of food items needed to fill single tin can.
Single tin can shoud heal 20 5F
This will allow to unify and compact food items;
Codevise - 28 lines, wont take much time, will do everything myself if canner TE source provided.