It's not surprising at all that the speaker, who was once an orphan literally starving in the streets, would be concerned with food. From his days scrabbling for scraps, to the bread he receives upon taking his vows at the monastery, to the Chianti that he glugs down on his forays into the Florentine night, Bro Lippo is firmly focused on the flesh, and his preoccupation with food is symbolic of this.
Lines 84-85: Here we get a grotesque description of the foods Little Lippo ate when he was an abandoned orphan in the streets. He gets the scraps that everyone else discards: skins of figs, melon rinds, and the peels of various vegetables—basically everyone else's trash.
Line 92: The poor little guy gets his first piece of bread in he doesn't know how long when his auntie takes him to the monastery. This bread represents how he becomes a monk not out of a true calling, but rather out of need. He needs to eat. And since the monk who takes him in is "fat," he's pretty sure he'll have regular meals if he takes those vows.
Line 103: Now a monk, he has a "good bellyful" of food. This contrasts sharply to the empty fruits (just the rinds and husks) that he previously dined on when he was lucky.
Line 339: The Chianti (a sort of red Italian wine) has loosened his tongue. Frolicking about and drinking wine is something a monk is not supposed to be doing, so the Chianti here (coupled with Lippo's outing) symbolizes the corruption of the Church and how hypocrisy is running rampant (Prior, we're looking at you—and your "niece").