1. IDENTIFYING MACROMOLECULES IN FOOD LAB

2. Introduction
Carbohydrates, proteins, and fats are all essential nutrients.
We cannot manufacture these nutrients, so we must obtain them from our environment.
The presence of these macromolecules can be detected by chemical indicators

3. Introduction
In lab, with the use of indicators as chemical detection tools, you will analyze a variety of foods for the presence of nutrients.
Detection is based upon observing a chemical change that takes place most often a change in color.

4. Objective Identify the presence of major nutrients in common foods
simple carbohydrates (glucose)
complex carbohydrates (starch)
Protein
Fat

5. What is an indicator?
Indicators are chemical compounds used to detect the presence of other compounds.

6. LAB SAFETY and CLEAN UP Loose Hair BACK
WEAR safety goggles and apron at all times
THOROUGHLY CLEAN lab area and equipment with plenty of water
NO GOOFING AROUND
Automatic Failure of LAB
NO EDIBLE products in lab
WORK at LAB BENCHES ONLY

7. Test for Simple Carbohydrates Benedict’s solution
Benedict's solution is a chemical indicator for simple sugars such as glucose: C6H12O6.
 yellow/green/brick red, etc.: positive test

8. Test for Simple Carbohydrates Benedict’s solution
Unlike some other indicators, Benedict’s solution does not work at room temperature - it must be heated first.

9. Procedure Simple carbohydrate
Add 5ml of food sample to test tube
Add 20 drops of Benedict solution
Place test tube in a hot water bath for 10 minutes.

10. Test for Complex Carbohydrates IKI solution
Iodine solution is an indicator for a molecule called starch.
Starch is a huge molecule made up of hundreds of simple sugar molecules (such as glucose) connected to each other.

11. Test for Complex Carbohydrates IKI solution
IKI solution  (Iodine Potassium Iodine) color change = blue to black

12. Procedure Complex carbohydrate
Add 5ml of food sample to test tube
Add 20 drops of IKI solution

13. Test for Protein (amino acids) Biuret solution
Biuret solution  dark violet blue to pinkish purple is positive for protein

14. Procedure Protein (amino acids)
Add 5ml of food sample to test tube
Add 20 drops of Biuret solution

15. Test for Fats (lipids) Sudan III
Like lipids, the chemical Sudan III is not soluble in water; it is, however, soluble in lipids.
In this test dark red Sudan III is added to a solution.
If lipids are present the Sudan III will stain them reddish-orange (positive test).

16. Procedure Fats (lipids)
Add 5ml of food sample to test tube
Add 20 drops of Sudan III
Stopper and gently shake (rock) the test tube.
If the the Sudan III color mixes with the solution it is a positive test

17. Additional Fat Test
Fats will leave a glossy, oily residue when wiped on paper.

18. Procedure:
Draw 6 squares on one side of your paper bag (5 foods + water)
With a fresh cotton swab, wipe a sample of the food to be tested in the square.
Let the paper dry.
Hold paper up to light and look for glossy, oily residue (use water as comparison).

19. Identification of Macromolecules in Foods FOOD INDICATOR Benedict
(Sugar)
IKI
(Starch)
Biuret
(Protein)
Sudan III
(Lipids)
Brown paper
Color
+/-
Apple Juice
Potato
Egg White
Veg Oil
Milk

20. Macromolecule Test Protocols Table
INDICATOR
MACRO-MOLECULE
- TEST
+ TEST
PROTOCOL
Benedict’s solution
IKI solution
Biuret solution
Sudan III
Brown paper

21. Procedure for Today Set up your notebook Go to your assigned station
Write the PROCEDURE down in your notebook
Make hypothesis which samples will test positive.
Gather Samples
Run Test & Record Results
Conclusion

22. Label & wipe on paper, let dry
Macromolecule Test Protocols Table
INDICATOR
MACRO-MOLECULE
- TEST
+ TEST
PROTOCOL
Benedict’s solution
simple carbohydrate
blue
Yellow, green, orange,
Red
5 ml +
20 drops + 10 min. bath
IKI solution
complex carbohydrate
gold
black
20 drops
Biuret solution
protein
violet, black
Sudan III
lipid
Light pink
reddish- orange
20 drops + rock
Brown paper
Lipid
No oily residue
Oily residue
Label & wipe on paper, let dry

23. Exit Task:
Why does the Sudan III not mix with the apple juice?