Identifying Organic Compounds In Foods.

Title of practical: Identifying organic compounds in foods.
DESIGN
OBJECTIVES:
• Determine whether specific nutrients are present in a solution of unknown composition
MATERIALS:

• 500 mL beaker
• Hot plate
• 9 test tubes
• Labeling tape
• Marker
• 10 mL graduated cylinder
• Benedict’s solution
• 9 dropping pipets
• Glucose solution
• Unknown solution
• Distilled water
• 9glass stirring rods
• Tongs or test tubes holder
• Test-tube rack
• Albumin solution
• Sodium hydroxide solution
• Copper sulfate solution
• Vegetable oil
• Sudan III solution
CAUTION:
• Put on a lab apron, safety goggles, and gloves. In this lab, you will be working with chemical that can harm your skin and eyes or stain your skin or clothing. If you get a chemical on your skin or clothing,wash it off at the sink while calling to your teacher. If you get a chemical in your eyes, immediately flush it out at the eyewash station while calling to your teacher.
• Do not touch the hot plate. Use tongs to move heated objects. Turn off the hot plate when not in use. Do not plug or unplug the hot plate with wet hands.
• Sudan III solution will stain your skin and clothing. Promptly washoff spills to minimize staining. Do not use Sudan III solution in the same room with an open flame.
BACKGROUND
1. In this investigation, you will use chemical substances, called indicators, to identify the presence of specific nutrients in an unknown solution. By comparing the color change an indicator produces in the unknown food sample with the change it produces in a sample of knowncomposition, you can determine whether specific organic compounds are present in the unknown sample.
2. Benedict’s solution is used to determine the presence of monosaccharides, such as glucose. A mixture of sodium hydroxide and copper sulfate determines the presence of some proteins. This procedure is called the biuret test. Sudan III is used to determine the presence of lipids.
VARIABLES
Dependent:Color change of the unknown solution at the end
Independent: Amount of organic compounds in the unknown solution
Controlled: Amount of indicator.
METHODOLOGY
Test 1: MONOSACCHARIDES
1. Make a water bath by filling a 500 mL beaker half full with water. Then, put the beaker on a hot plate, and bring the water to a boil.
2. While you waiting for the water to boil, label one test tube “1 –glucose”. Label the second test tube “1 – unknown”, and label the third test tube “1 – water”. Using the graduated cylinder, measure 5 mL of Benedict’s solution, and add it to the “1 – glucose” test tube. Repeat the procedure, adding 5 mL of Benedict’s solution each to the “1 – unknown” test tube and “1 – water” test tube.
3. Using a dropping pipet or eyedropper, add 10 drops of glucose solution to the “1– glucose” test tube. Using a second dropping pipet, add 10 drops of the unknown solution to the “1 – unknown” test tube. Using a third dropping pipet, add 10 drops of distilled water to the “1 – water” test tube. Mix the contents of each test tube with a clean stirring rod. (It is important not to contaminate test solutions by using the same dropping pipet or stirring rod in more than onesolution. Use a different dropping pipet and stirring rod for each of the test solutions).
4. When the water boils, use tongs to place the test tubes in the water bath. Boil the test tubes for 1 to 2 minutes. Use tongs to remove the test tubes from the water bath and place them in the test-tube rack. As the test tube cool, an orange or red precipitate will form if large amounts of glucose are present.If small amounts of glucose are present, a yellow or green precipitate will form.
Test 2: PROTEINS
1. Label one clean test tube “2 – albumin”, label a second test tube “2 – unknown”, and label the third test tube “2 – water”. Using a dropping pipet add 40 drops of albumin solution to the “2 – albumin” test tube. Using a second dropping pipet, add 40 drops of unknown solution to the “2 –...