You Become What You Eat:
What's in There?
Vitamin C in Fruit Juice

Introduction You already know that certain compounds in foods are required for good health, for example, the familiar nutrients like proteins, fats, carbohydrates, vitamins, and minerals. In this module, you have been introduced to other compounds called phytochemicals. Many of those phytochemicals are important because of their antioxidant activity.

Menu General Safety Guidelines Background on Titration Microscale Notes Procedure Data Analysis and Conclusions

You may have already learned that it is not simply the foods you eat that provide nutrients and energy, but that it is the specific compounds in those foods. Since most foods are a complex mixture of compounds, how have researchers analyzed foods to determine the many different compounds within them? This lab will allow you to use a common procedure used for many chemical analyses, including those for foods. The procedure is called a titration. In this lab the titration will be done on a microscale basis.

The chemical substance studied in this lab is vitamin C, whose chemical name is L-ascorbic acid. Vitamin C is an antioxidant. It is not, however, usually considered a cancer-related phytochemical since it has not been shown to have anticancer activity. It does, of course, protect against scurvy, and diets high in vitamin C have been closely associated with general health.

Background on Titration

A titration is a method of observing a chemical reaction to determine the exact quantities of each reactant that are involved in a reaction. In analysis by titration, a known quantity of a solution of substance A is slowly dripped into solution B until the reaction reaches the end point. If necessary, a chemical indicator is added to substance B to visualize the end point more easily. By knowing the concentrations of the two solutions, and by measuring the volume of each solution, we can calculate the quantities of both A and B that entered into the reaction.

Microscale Notes

In a microscale investigation, you use small quantities of materials. Reactions takes place in microplates. Reagents are dispensed in micropipettes, sometimes called Beral pipettes. Solutions you will need are:

• Vitamin C solution (concentration = 1 mg/ml)
• Iodine solution
• Starch solution
• Fruit juices containing vitamin C