I would do two things. First, keep them separate whenever you are handling food, and even feed them on opposite sides of the room. Second, I'd find a behaviorist in your area. This CAN be trained away, but you have to do so deliberately, consistently, and carefully.

And it is best to do so now, while the future baby is still safely inside. You want to get the training now, and keep reinforcing it, so when your baby is a toddler, the issue is well under control.