the cooking set removes 10%, and the rest is from the cooking title and the poison resistance title, also if you do recipes I believe they are not counted as poisonous.
to evolve the picky eater title you have to throw away food, 500 times for max level.
and for the poison title you have to get poisoned, 20000(eating poisoned stuff or getting hit by poison traps on dungeons) and die from poison 4 times for max level.
edit: for the cooking title you need to cook 1000 meals for it to go max level.