Key Concept: Food tests identify glucose, starch, protein, and lipids using simple chemical reagents.
Section A: Tests
1. Describe the Benedict's test for glucose, including the positive result. [3]
2. Describe the iodine test for starch, including the positive result. [2]
3. Describe the Biuret test for protein, including the positive result. [3]
4. Describe the emulsion test for lipids, including the positive result. [3]
Section B: Planning
5. Outline a simple plan to test a food sample for all four nutrients. [4]
Total marks: 15
Mark Scheme
1. Add Benedict's solution, heat in hot water bath; blue to green/yellow/orange/brick-red if glucose present [3]
2. Add iodine solution; yellow-brown to blue-black if starch present [2]
3. Add Biuret reagent (NaOH then CuSO4); blue to lilac/purple if protein present [3]
4. Shake with ethanol, then add water; white emulsion if lipid present [3]
5. Grind sample with water, split into test tubes, perform each test separately with controls and record results [4]