Vitamin C in Juices

Experimentation with Vitamin C

Determine the Vitamin C content in various freshly squeezed fruit juices. Compare kiwis and oranges (really high) to peaches or apples (really low). Or, blend a vegetable in water to create a solution that can be tested. You will want to use cheesecloth to remove the fiber from the solution. Fiber is a good for you too by the way. 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 I3 - ; 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:

(number of drops to fruit juice) / (number of drops to Vitamin C standard), recorded in mg.

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)