Vitamin C in Juices

Experimental outline

Determine the Vitamin C content in various freshly squeezed fruit juices. Compare kiwis and oranges (high concentration of Vitamin C) to peaches or apples (low concentration of Vitamin C). Or, blend a vegetable in water to create a solution that can be tested. Use cheesecloth or fiber to remove the fiber from the solution. Bell peppers are particularly high in Vitamin C but the green ones are supposed to have higher content than the red or orange ones. The Natural Hub has we page that lists the Vitamin C content of many fruits at: http://www.naturalhub.com/natural_food_guide_fruit_vitamin_c.htm

Materials

1. Fruit juices and fruit drinks containing vitamin C (use 1.00 mL per experiment)
2. Vitamin C Standard solution (1 mg/mL)(use 1.00 mL per experiment)
3. Starch solution (sue 1.00 mL per experiment and control for 2.00 mL total)
4. Iodine solution (we actually make I^3-; need up to 1.00 mL per experiment, so need 2.00 L)

Procedure for fruit juice or drink

1. Carefully squirt 1.0 mL of fruit juice or drink into a 10 mL graduate cylinder
2. Carefully squirt 1.0 mL of starch solution in to the same 10 mL graduated cylinder
3. Empty the contents of the cylinder into a small Erlenmeyer flask.
4. Use a pipet bulb to add the iodine solution.

Count the number of drops it takes to form a purple color.

Swirl the flask to make sure the solution stays purple. If it doesn’t, add one more drop.

1. Report your number of drops to the assistant.
2. Repeat the procedure with the vitamin C standard

Procedure for vitamin C standard

1. Carefully squirt 1.0 mL of vitamin C standard into a 10 mL graduated cylinder
2. Carefully squirt 1.0 mL of starch solution into the same 10 mL graduated cylinder
3. Empty the contents of the cylinder into a small Erlenmeyer flask.
4. Use a pipet bulb to add the iodine solution.

Count the number of drops it takes to form a purple color.

Swirl the flask to make sure the solution stays purple. If it doesn’t, add one more drop.

1. Report your number of drops to the assistant.
2. You can calculate the mg vitamin C from the following equation:

Amount of Vitamin C (mg)=(number of drops to fruit juice) / (number of drops to Vitamin C standard)

The equation above has been simplified from this equation Estimated Vitamin C content = (1 mL) x (1mg/mL) x (number of drops to fruit juice) / (number of drops to Vitamin C standard)