Required Practical: Food Tests
Identifying Nutrients in Food Samples
General Preparation for Food Tests
- Start by breaking down the food using a PESTLE AND MORTAR.
- Transfer the ground food into a BEAKER with distilled water.
- STIR the mixture to dissolve some food particles.
- FILTER the mixture to remove solid residues.
Testing for Sugars: BENEDICTS REAGENT
- Add the food sample to a test tube, mix in Benedict's solution.
- Heat the tube in a WATER BATH at 75°C for 5 minutes.
- A colour change indicates the presence of reducing sugars, with the colour varying from BLUE to GREEN to YELLOW or BRICK-RED depending on sugar concentration.
Testing for Starch: IODINE SOLUTION
- Place the sample in a test tube and add iodine solution.
- A colour change from BROWN-ORANGE to BLUE-BLACK signifies the presence of starch.
Testing for Proteins: BIURET TEST
- Combine the food sample with Biuret solution in a test tube.
- Gently shake; a change to PURPLE indicates protein. If no protein, the solution remains BLUE.
Testing for Lipids: SUDAN III TEST:
- Add the food sample and Sudan III stain solution to a test tube without filtering.
- Gently shake the tube. Lipid presence will show as a separate BRIGHT RED LAYER.
