Biology
Mr. Galego
TESTING FOOD FOR NUTRIENTS
INTRODUCTION:
In this experiment you will evaluate the nutrient content of unidentified food samples. You will use chemical indicators to test
unknown food samples for specific nutrients. By comparing the color change the indicator produces in the unknown with the
change it produces in the known nutrient, you can estimate the amount of that nutrient. Use small (pea-sized) samples.
MATERIALS:
400-ml beaker
Hot plate
8 test tubes
Test tube rack
4 medicine droppers
Test tube holders
Unknown food substances
Glucose
Cornstarch
Powdered egg white
Vegetable oil
Distilled water
Benedict's solution
Biuret solution
Sudan III solution
PROCEDURE:
5
Sugar Test
1. Fill a 400-ml beaker to about 300 ml with water and heat on the hot plate. Be sure to label all test tubes.
2. Place pea-sized portions of glucose and the unknown substance you are testing in separate test tubes. Add about 2 mL of
distilled water and about 30 drops Benedict's solution to each test tube. Hold the tube between the thumb and index finger of
one hand, thump it with the middle finger of the other hand to mix the contents of the test tube.
3. When the water boils, use test tube holders to place the test tubes in the water bath. Leave the test tubes in the water bath
for 5 minutes. Do not let the water bath boil hard. Control the boiling by turning the hot plate on and off as needed.
4. Remove the test tubes with holders and place the tubes in a test tube rack. Unplug the hot plate to cool. Observe the
results and record your observations in the DATA TABLE.
Starch Test
5. Place pea-sized portion of cornstarch in a clean test tube and some of the unknown substance in another Add about 5 ml
of distilled water and 10 drops of iodine solution to each test tube. Thump to mix. Observe the results and record in the DATA
TABLE.
Protein Test
6. Place pea-sized portion of powdered egg white in a clean test tube and some of the unknown in another. Add about 3 ml of
distilled water and about 30 drops of Biuret solution to each test tube. Thump to mix. Observe the results and record in the
DATA TABLE.
Lipid Test
8. Add a small amount of vegetable oil to a clean test tube and some of the unknown in another. Add about 5 ml of distilled
water and thump to mix. Add 20 drops of Sudan III solution to each test tube. Thump to mix. Observe and record your results
in the DATA TABLE.
9. Repeat steps 1-8 for the second unknown food item.
DATA TABLE:
Mark your results in the appropriate boxes. Indicate relative amount by H for high, M for medium, L for low, or 0 for
none. Note that the color of the known food tested indicates a HIGH level of that nutrient and the original color of the
reagent indicates NO nutrient.
Sugar Test
SUBSTANCE
RELATIVE AMOUNT
glucose
H
Starch Test
SUBSTANCE
RELATIVE AMOUNT
cornstarch
H
unknown A
unknown A
unknown B
unknown B
Protein Test
SUBSTANCE
RELATIVE AMOUNT
egg white
H
SUBSTANCE
vegetable oil
unknown A
unknown A
unknown B
unknown B
Lipid Test
RELATIVE AMOUNT
H
CONCLUSIONS:
1. Using your nutrient data, match each unknown food to its correct food label below. For each, provide a 1-2-sentence
explanation that considers the presence or absence of each nutrient tested. Hint: starch = total carbohydrates –
(sugars + dietary fiber)
Nutrition Facts
Nutrition Facts
Amount Per Serving
Amount Per Serving
Calories from Fat 0
Calories 150
Calories from Fat 4
Calories 86
% Daily Values*
Total Fat 0g
Saturated Fat 0g
Cholesterol 0mg
Sodium 0mg
Total Carbohydrate 36g
Dietary Fiber 3g
Sugars 30g
Protein 2g
0%
0%
0%
0%
12%
12%
% Daily Values*
Total Fat 0.44g
Saturated Fat 0g
Cholesterol 5mg
Sodium 128mg
Total Carbohydrate
12g
Dietary Fiber 0g
Sugars 12g
Protein 8g
1%
1%
2%
5%
4%
0%
2. Using your data and observations, create a hypothesis for the identity of each unknown food. Give reasons to
support your hypothesis.