Group Members:
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Identifying Basic Nutrients in Food (40 pts)
Purpose
Do you know what nutrients are in the bread you toast for breakfast and the banana you eat for lunch? This
experiment will help you find out as you test a few common foods for the presence of complex
carbohydrates (starches), simple carbohydrates (sugar) fats, and proteins.
Equipment and Materials
Hot plate
Brown paper
Wash bottle
8 paper cups
1 plastic spoon
1 200-mL beaker
1 test tube rack
5 test tubes
1 10-mL graduated cylinder
Iodine solution
Benedict’s solution
Biuret reagent
Egg white
Vegetable oil
Starch suspension
Dextrose suspension
Bread suspension
Banana suspension
Potato flakes suspension
Fat-free milk
Whole f at milk
Procedure: Part A
1. Take about 15 ml of starch suspension, dextrose suspension, and egg white in separate paper cups.
2. Place four clean test tubes in a test tube rack. Place a piece of paper underneath the test tubes rack
and label the test tubes starch, dextrose, egg white, and water on the paper.
3. Add 3 ml of starch suspension, dextrose/sugar suspension, egg white, and water in each test tube.
4. To each test tube, add 3 ml of Benedict’s solution. Place the test tubes in a 200-mL beaker
containing enough water to complete surround the contents of the test tubes. Heat the water to
boiling for three minutes. Record any color change.
5. Thoroughly clean the test tubes using soap. Repeat step 3.
6. Add 3 ml of water to each of the first three test tubes containing starch suspension, dextrose
suspension, and egg white. Then add 5 drops of Biuret reagent to all four test tubes. Record any
color change.
7. Thoroughly clean the test tubes using soap. Repeat step 3.
8. To each of these test tubes add one drop of iodine solution. Record any color change.
9. Fats don’t dissolve in water; a different test is needed to check for their presence. Place a drop of the
starch suspension, dextrose suspension, egg white, and a drop of vegetable oil on a brown paper.
10. Hold the paper up to a light. Any sample containing fat will produce a translucent spot on the paper.
Describe the appearance of each sample in the data table.
Nutrients
Tested
Reagent Used
Iodine Solution
Benedict’s Solution
Biuret Reagent
Brown Paper
Starch
Dextrose
Protein
Water
Fat
(8 pts.)
Procedure: Part B
11. Obtain samples of toast, banana, potato flakes, fat-free, and whole fat milk in separate paper cups.
12. Add water to the solid samples to make bread, banana, and potato flakes slurries using a plastic
spoon. Make sure your clean the spoon between samples.
13. Place 5 clean test tubes in a rack. Obtain 3 ml of each food sample in the test tubes. Test with
Benedict’s solution as in step 4. Record results.
14. Clean the test tubes and place fresh samples. Test with Biuret reagent as in step 6. Record results.
15. Clean the test tubes and place fresh samples. Test with iodine solution as in step 8. Record results
16. Using a small amount of each of the five food samples, test for the presence of fat on a piece of
brown paper. Record results.
Samples
Tested
Reagent Used
Iodine Solution
Benedict’s Solution
Biuret Reagent
Brown Paper
Bread
Banana
Potato flakes
Whole Milk
Fat-Free Milk
(10 pts)
Clean Up (5 pts.)
17. Through away all food samples, paper cups, plastic spoons, and other trash in the trash can. (1)
18. Clean all equipments with soap and return to the teacher. (2)
19. Your station and table top is clean and dry. (1)
20. The sink(s) you used is free of food sample, clean and dry. (1)
Pre Lab Questions
1. What is the purpose of Procedure: Part A? (1)
2. What nutrients (starch, sugar, protein, and lipids) would you expect to find in each of the 5 food
samples tested? (4)
Analyze and Conclude
1. With what nutrient did each reagent react? What color changes indicated this? (4)
2. What can you conclude about the nutrient content of each food tested? Do the results agree with
your prediction? (4)
3. Did any foods seem to contain only one type of nutrients? Explain.(2)
4. How do whole milk and fat-free milk differ in nutrient content? (2)\
5. On a scale of 1 to 10, rate this lab in terms of difficulty. (1 = easy; 10 = difficult)
6. On a scale of 1 to 10, rate this lab in terms of enjoyment. (1 = boring; 10 = fun)