The item tested in the test to do the reaction with potassium permanganate is easy oxidizable substances, mainly from the product was extracted by the leaching solution dissolved out of the easily oxidizable organic matter, if too much of these substances, may be harmful to the body.
Of course, there are some more difficult to oxidize the material, it is not the test of this project. Some products require that the hard-to-oxidize and easy-to-oxidize substances can be tested by the total organic carbon test method.