What 'flesh' and 'blood' was Jesus referring to? (catholics only please)?

When Jesus spoke of eating his flesh and blood, many turned away from him because they could not hear it. But what was the flesh and blood he was referring to? Would Jesus have objected if someone came up to him and bit him (sorry I can't put that better). I'm not sure if this is the catholic view, but some interpretations say that he was actually referring to his 'perfect' body and not his 'mortal' body. Would that mean that the ceremony of communion wouldn't be valid until after the rise to heaven?