It may also be a joke reference to one of Jack's lines in the original prequel story she debuted in. In the story she tells Reika that she prefers eating the souls of evil people as they taste better to her. So pure, virtuous hearts would probably smell/taste bad to her by that logic.
Stinks of monkey...
This whole heart farce is a full reference to Journey to the West, specifically, the chapter of Kingdom of Biqiu.
In this chapter, the king of Biqiu gradually fell sick under the influence of his newlywed wife, a White Faced Vixen Spirit under the disguise of a fair maiden. Desperately in need of a cure, the king believed the lie of the royal father-in-law, who was actually a White Deer Spirit in disguise, and issued an order to capture 1,111 children, attempting to make the cure with their hearts.
After the protagonists arrived in Biqiu, the royal father-in-law told the king that Tang Sanzang's heart was the best cure, so the king ordered Tang Sanzang to be arrested and disemboweled. Anticipating the enemy's plan, Sun Wukong the Monkey King disguised himself as Tang Sanzang and was imprisoned instead.
When presented to the king, Sun Wukong disemboweled himself and revealed a dozen hearts as referenced in the comic, effectively frightening both the king and the royal father-in-law. Sun Wukong then pointed out that none of his many hearts was an evil black heart, but the royal father-in-law did have one. Under the threat of evisceration, the royal father-in-law's true form was exposed and ran in fear. His fake daughter was soon slain by Zhu Bajie, and he was subdued and returned to his rightful master, the Old Man of the South Pole.
How do they taste?Jack The Ripper 2I was totally messed up by a Saber who totally should be a Berserker....Gotta go home and have me some hearty recovery snacks...Someone gave me a lot of hearts today.Wow! That's a lot!This is the heart of Buddha for freeing people from torment.This is the heart of sincerity for worshiping Buddha and seeking Sutra.This is the heart of compassion for empathizing with others.This is the heart of mercy for keeping people from harm's way.This is the heart of loyalty that simply won't give up.This is the heart of determination for eliminating evil from the world.All are good hearts, and not a single black heart within.