Ketchup Simulation in Blender

I’m a newbie in CG-Art and working on a model of a burger in Blender. However i’ve come across a problem when letting Ketchup flow over my burger. I have a stripe of salad (made by converting two nurbs curves into a mesh and filling the space between them), whose collision-detection doesn’t let the ketchup touch them but stops it to far away from them. Any ideas on how to fix this ? And btw. i’d also be thankful for tips on how to give a liquid a more ketchup’ish feel.
Thx =)