Tests for the presence of carbohydrates, proteins and lipids. By Sophie Fox

STARCH

• Add a solution of iodine (in potassium iodide).
• The iodine solution changes from yellow to blue/black.

REDUCING SUGARS

• Heat with Benedict's solution (alkaline copper sulfate).
• The colour changes from blue to orange/red.
• A precipitate is formed.

NON-REDUCING SUGARS

• The non-reducing sugar will not react with the Benedict's solution.
• Boil the sample with hydrochloric acid.
• This hydrolyses any sucrose present, splitting sucrose molecules to give glucose and fructose monosaccharides.
• Cool…