It's a predatory instincts thing, I assume? It wasn't quite right for my friend, either. He had to supplement it with fresh human blood to - to take the edge off, you know?

[ Which has had the neato side-effect of desensitising Angel to this stuff and ensuring there isn't even a flicker of judgement or revulsion at Zombie Cannibal Murderchild. Score!! ]

It may not work, but it might be a good starting point. You can see how much it helps, then try other ideas on top of it. Like... uh, Iunno. Holding your nose? Though that'll make you sound kinda silly.