While you are learning the behaviour, I would definately keep rewarding with food...
I always give a food reward for a good recall even now - Honey has had a pretty solid recall since she was young, but it's not something I ever take for granted. We practise it at some point on most walks, and she always gets a good food treat (or her ball, which in her mind is even better).
If she does a poor recall (gets distracted or ignores me) I get her to me and just praise this - then I follow up with an easy recall for a good reward, just to keep the motivation up...
It's up to you if you want to phase out food treats in time, but while learning I would definately keep the rewards coming...
It's worth seeing if there is a toy/game she really enjoys which can be a recall reward, as I suspect for most dogs a bit of a fuss isn't going to compete with the thrill of chasing something...
