Oeznik probably is questioning Zemo just as much as Bucky - he did marry the man shameless enough to eat out of the trash, really. What does that say about him?

"Oh, I've had it before... I'm simply enjoying watching you eat it." Not that Bucky is overly picky about his food, but it is amusing to see what reactions flit across his face.

"I suppose a bite wouldn't hurt. Would you like some of mine?" It is a rather tame dish by comparison...