Titrations of Ascorbic Acid

The experiment was meant to determine which factors in the normal everyday life would allow orange juice to have the highest ascorbic acid (vitamin C) content. The factors tested were the absence/presence of pulp, the absence/presence of light, and application of heat.

Johnston and Modrich first made their samples according to the standard three factor DOE setup. They titrated the samples using an iodine .05M solution, and a commercial starch in water suspension as an indicator. The recorded iodine amount needed to produce a reaction was used to calculate into actual amount of ascorbic acid in samples. The best result was calculated from their sample of pulp, light, and heat (+,+,+), which disproved their hypothesis of pulp, no light, and heat (+,-,+). An actual measure of .53g/L of ascorbic acid was calculated in that experiment. There were two trials, (-,+,+) and (-,-,+), which had the lowest calculations. For both low trials, pulp was absent; for the highest trial, pulp was present. Pulp's presence in the solutions seemed to be the factor that affected the trials the greatest. Singularly and on average, heat and light had no effect, but together, all the variables interacted.

Research Done By:

Elizabeth Johnston

Dan Modrich