What is the Shelf Life of Natural or Processed Vitamin C?

Difficulty of Project (Easy, Medium, Hard)

Hard

Grade Level (Elementary, Middle, High School)

High School Cost

Approximate Cost

$8-$25

Safety Issues

Iodine and potassium iodide are chemicals used in this experiment. A designated supervisor such as an adult, parent, or guardian should supervise the experiment. Gloves and protective goggles should be worn to reduce the chance of staining and/or chemical burns that may result from a spillage. Material Availability (Are the materials required readily available?) The equipment for the project can be found in a high school laboratory. Iodine and potassium iodide can be purchased from a chemical supply catalog. The juices and corn starch can be purchased from the local grocery store.

Approximate Time Required to Complete the Project (Hours, days, weeks)

4-8 weeks

Objective

To investigate the rate of vitamin c degradation in natural and processed orange juices.

The project goals include measuring the concentration of vitamin c in organic and processed orange juices and determination of the subsequent change in vitamin c concentration over time.

Materials and Equipment / Ingredients

Introduction

Vitamin C is naturally produced by citrus fruits and is an essential nutritional organic compound. Vitamin C like other organic compounds deteriorates over time. Oxidants react with the functional groups of the vitamins causing bonds to distort and the functional shape to lose its original structure. Shape in nature is related to function. As shape changes, the function of the substance changes. Indicators are chemicals that change color in response to chemical change. In this experiment a starch-iodine indicator is used to indirectly estimate the concentration of vitamin c in organic and processed orange juices. The starch-iodine indicator will change from colorless to blue/black in the presence of vitamin c. In this titration, the volume of indicator added in solution relates to the volume of vitamin c in the orange juice.