Was going to say the same thing. The first answer is "human" a really old riddle. The answer given has nothing to do with the first riddle and I feel I heard that answer before but can't think of the riddle it's attached to.
The salt's riddle is usually accounted to story about Tokugawa Ieyasu (but they might also import it from the mainland).
"What is the best and worst tasting thing in this world?"
Tokugawa asked
one of his wives, "What is the most delicious thing in the world?", and she answered salt, because even with any exotic ingredient, it will depend on how you season it with salt. And then Tokugawa asked, "Then what is the most terrible tasting thing in the world?" and she answered it's also salt, because no matter how good the food is, it became inedible with too much salt.
Checking the manga raw, the daughter actually only ask "what is the most delicious thing", and Kong Ming smiled, thinking how this is not what he expected. He probably understand the riddle, so he explained not just the most delicious, but also the worst food even before she followed up the question.
And yes, those who complained about "not pretty" should read
Otong's reply which also gives context on why Astaroth thinks it have to be Kong Ming.