1. Unknown Foods: Macromolecule Lab Chapter 2: Carbohydrates, Lipids, and Proteins

2. Objectives Use chemical indicators and other tests to determine the presence of macromolecules in foods Identify the presence of organic macromolecules in foods found in the diet

3. Procedure Perform four tests on food samples to determine the presence of – Lipids – Sugar – Protein – Starch Record the results of each test in the data table Clean all glassware before changing stations

4. How to test for lipids Fold a piece of paper into small squares Label each square with the name of the food sample Rub a small amount of each food on the paper Let the paper dry Hold the paper up to the light

5. Positive Lipid Test Lipids will cause the paper to become translucent – Light will pass through the paper Wet paper is not a positive test If paper stays opaque – the test is negative – Opaque means light does not pass through

6. Test for Starch Place a small amount of each food in a petri dish Add 2 drops of iodine to the sample Observe the color of the iodine and record in the data table

7. Positive Starch Test If starch is present, iodine will turn a purple/black If there is no starch, the iodine stays red

8. Test for Sugar Pour 5 mL Benedict’s solution into numbered test tubes with a small amount of each food sample Place the test tubes in a boiling water bath, heat for 1 minute and observe color changes Record results in data table

9. Positive Sugar Test Benedicts Solution will change from blue to orange or green in the presence of sugar

10. Test for Protein Place a small amount of each food in a petri dish Add 3 drops of Biuret to each food Observe any color change and record results in data table

11. Positive test for Protein Biuret solution will change from blue to pink or purple in the presence of protein