I googled "food of love" and found this reference to a song of Henry Purcell (1659-1695). The lyrics were written by Col. Henry Heveningham

If music be the food of love,
sing on till I am fill'd with joy;
for then my list'ning soul you move
with pleasures that can never cloy,
your eyes, your mien, your tongue declare
that you are music ev'rywhere.

Pleasures invade both eye and ear,
so fierce the transports are, they wound,
and all my senses feasted are,
tho' yet the treat is only sound.
Sure I must perish by our charms,
unless you save me in your arms.

I suppose that Darcy and Elizabeth would be acquainted with it.