Name: __________________
Date: ___________________
Living Environment
Lab # ____
Testing for Sugar, Starch and Proteins in Foods
Purpose: To identify certain biological molecules in food materials using indicators
Hypothesis: ?????????
Materials: ???????
Procedure:
Testing for starch:
1. Take a piece of bread and potato and place it on a paper towel. Take
a small amount of egg white and add an equal amount of water. Place the
solution in a test tube.
2. Place 3 drops of Lugol’s solution on the bread and potato.
Place 10 drops of Lugol’s solution in the egg white solution.
Record what happens in data table #1.
Testing for Glucose:
1. Label 3 test tubes A, B and C.
2. Take a small amount of egg white, corn syrup and milk and
place all three samples in three test tubes. Add an equal amount of water
3. Place 20 drops of Benedict’s solution in the test tubes. Stir.
4. Place all three test tubes in a hot water bath and observe what happens
5. Record your results in Data table #2.
Testing for Protein
1. Place a small amount of egg white, corn syrup and milk in three test tubes.
Add an equal amount of water. Be sure to label all test tubes.
2. Add 20 drops of Biuret’s solution to each test tube. Stir.
3. Record your data in chart #3.
Data Table #1
Food
Indicator
Original Color
Color change/
Starch Present?
Indicator
Original Color
Color after heating/
Glucose present?
Data Table #2
Food
Data Chart #3
Food
Indicator
Original Color
Color after heating/
Protein present?
Questions:
1. Explain how you can tell whether a food contains starch? Where does starch come
from?
2. Explain how you can tell whether a food contains sugar?
3. What type of nutrient is starch and sugar? Which is complex? Which is simple?
4. What is a practical use for this kind of testing of food products?
5. What are two other foods that would test positive with Biuret solution? Would the
color of the food interfere with determining a positive or negative result?
Conclusion:
Write a paragraph on what you have learned from this lab. Remember to refer back to
the hypothesis.