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United States Department of Agriculture

Agricultural Research Service

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Comparing Vitamin C Content

With the method here, you can compare relative vitamin C content and rank fruits, juices and beverages from highest to lowest, but you won't be able to get exact quantities.

You'll need some 2% iodine solution (find it at your local pharmacy) to prepare the vitamin C indicator solution described in steps 1 to 4.

1. Mix 1 tablespoon of cornstach into enough water to make paste.

2. To this paste, add 250 milliliters of water and boil for 5 minutes.

3. Add 10 drops of the starch solution to 75 milliliters of water (use an eyedropper).

4. Add enough iodine to produce a dark purple-blue color. Now your indicator solution is ready.

5. Put 5 milliliters of indicator solution (about 1 teaspoon) in a 15-milliliter test tube (one for each sample).

6. To the test tube, use a clean eyedropper to add 10 drops of juice from the fruit or beverage (for solids, pulp them in a blender and strain the juice). Re-clean the eyedropper for each sample.

Hold the test tube against a white background.

Line up the tubes from lightest to darkest purple. The lighter the solution, the higher the vitamin C content. That's because vitamin C causes the purple indicator solution to lose its color.

Last Modified: 8/12/2016
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