Start of Method for ALL
- First take the food sample and grind with distilled wate using a mortar and pestle to make a paste
- Transfer paste to beaker and add more distilled water and stir so the chemicals in food dissolve in the water
- Filter solution to remove suspended food particles EXCEPT WHEN TESTING FOR LIPIDS
Iodine Test for Starch
- Place 2cm
of food sample into a test tube - Then add a few drops of iodine using pipette
- If starch is present the solution turns from brown to Blue-Black
Benedict’s Test for Reducing Sugars
- Place 2cm
of food sample into a test tube - Add 10 drops of Benedict’s solution
- Place in a hot water bath
- If reducing sugar is present a precipitate is formed and the solution will change colour. Colour tells you how much sugar there is:
- Green - low, Yellow - medium, Red - high
Test for Protein
- Place 2cm
of food sample into a test tube - Add 2cm
of blue biuret solution - If protein is present to solution will change to a purple or lilac colour
Test for Lipids
- DO NOT FILTER SOLUTION AFTER GRINDING IN MORTAR AND PESTLE
- Place 2cm
of food sample into a test tube - Add a few drops of distilled water and ethanol
- Gently shake solution
- If lipids are present a white cloudy emulsion forms