Ascorbic acid or vitamin C is a powerful antioxidant nutrient that is found naturally and also added to fruit juices for its health benefits. According to a study published in 2000 in the journal "Food Chemistry," the ascorbic acid content of juice in closed containers has a somewhat temporary shelf-life, decreasing at a rate of 29 to 41 percent over four months at room temperature. Refrigerated juices, including fresh orange juice also lost some of its vitamin C content. One method to measure the amount of ascorbic acid in juice involves a complex chemical reaction and calculation.
Step 1
Estimate the amount of ascorbic acid lost from a carton of juice by noting the packaging date. Calculate how long the juice has been on the shelf and estimate the current vitamin C content, according to the research study published in the "Food Chemistry" journal. For example, if the juice is three months old, the estimate nutrient loss, according to the study, would be less than approximately 29 to 41 percent.
Step 2
Use a chemical reaction to measure the amount of ascorbic acid in juice. Prepare a iodine-cornstarch solution by dissolving 1 tbsp. of cornstarch with 2 tbsp. of water in a saucepan over heat. Add 1 cup of water and bring the solution to a boil.
Step 3
Pour 75 ml distilled water into a separate container, and add 10 drops of the cornstarch solution. Use an eyedropper to add iodine to the diluted cornstarch solution slowly, until it takes on a deep purple color. In a test tube or small container, add approximately 5 ml of the iodine indicator solution. Add up to 15 drops of juice to this and gauge the color. The lighter the color of the iodine solution, the greater the ascorbic acid content.
Step 4
Add approximately 5 ml of the iodine indicator solution into a test tube or small glass container. Add up to 15 drops of juice to this and gauge the color. The lighter the color of the iodine solution, the greater the ascorbic acid content.
Tips and Warnings
- A chemical reaction outlined by the Royal Society of Chemistry can more accurately measure ascorbic acid content in juice. However, this method is complex and requires laboratory equipment. It involves combining iodine with juice and titrating this solution with sulfuric acid. The titre volume will then show the amount of ascorbic acid.
- Wear gloves and a mask when handling substances such as iodine and sulfuric acid. Carry out the reactions in a well-ventilated space, and avoid inhaling these chemicals.
Things You'll Need
- Juice
- Iodine solution, 2 percent
- Sulfuric acid solution
- Test tubes
- Ceramic bowl
- Small pan
- Eye dropper
- Bunsen burner or stove
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