Now, repeat the experiment with a bottle of red wine. No bang is necessary. Clearly, it is more than taste and culture that distinguishes ketchup from wine. This is what the science of complex fluids is about. Complex fluids are those fluids, which are not simple.
Simple fluids are fluids with a simple description, and many such fluids like water or wine, exist.
They may all be described quite elegantly with the same equation. Most real fluids have aspects of complexity once you look carefully enough. For example, it makes a big difference whether you use oil or water to lubricate your car engine. Such complex behavior may be explained when you look at the very smallest scales where things start to jiggle about because of Brownian motion. Or, if you look at a fluid interface, like that in a bottle of oil-water salad dressing you will usually find a whole forest of little molecules that like to be right at the interface and change its properties.