Two separate tests for lipids...why?

Question

The Brown paper one, and the one where Sudan IV reagent is added...but what is the advantage? Thanks alot guys.
There is a similar question in the archives but wanted to see what others have to say. Thanks a bunch.

Answer 1

Sudan IV is a dye insoluble in water but soluble in lipids. So first you arrange to separate the lipid layer from the weater layer in atest tube. Add sudan IV, and the lipid layer adopts an orange-red color.

Brown bag test: Put a drop or so of sample on a square cut out of a brown paper bag. Heat under a heat lamp. If you still have a dark stain on the brown paper, it's lipid.

The advantage is that the sudan IV dye test lets you know more exactly that the substance is hydrophobic and lipid.