Esculent - 1. Something edible, especially a vegetable. 2. Suitable for use as food; edible.
When people thought of a culinary expert, they usually thought of Molly Weasley. After all, with six boys in the house, tables groaning with delicious cooking were her specialty. No one ever thought of Luna Lovegood.
Yet Luna was cleverer than most people gave her credit for. Especially when it came to food. Roaming the moors looking for strange creatures, either alone or with her father, had taught her something.
The House Elves at Hogwarts taught her too; both how to cook and the fact that food could lead to having friends.
Yes, Luna was most definitely a food expert.