When digested, proteins provide amino acids, carbohydrates provide sugars, fats provide fatty acids. Theory Starch, a carbohydrate, can be identified by a positive iodine test. A few drops of iodine solution are added to a raw or boiled sample of the substance suspected of containing starch. If starch is present, the substance will turn blue-black in the area where the iodine solution touches it. Substances with very small amounts of starch will turn faint blue or greenish instead of blue-black.
Many biodegradable materials have a high starch content.
These materials can be identified with the iodine test. Like starch, sugars are carbohydrates. They are also saccharides a class of chemical compounds. The term saccharide derives from the Greek sakkharon , meaning sweet. The saccharides range from simple compounds, monosaccharides, to large complex molecules, polysaccharides.