Vitamin C Determination by Indophenol Method

Abstract

Vitamin C is an essential nutrient in the diet, but is easily reduced or destroyed by exposure to heat and oxygen during processing, packaging, and storage of food. The U.S. Food and Drug Administration requires the Vitamin C content to be listed on the nutrition label of foods. The instability of Vitamin C makes it more difficult to ensure an accurate listing of Vitamin C content on the nutrition label.

The official method of analysis for Vitamin C determination of juices is the 2, 6-dichloroindophenol titrimetric method (AOAC Method 967.21). While this method is not official for other types of food products, it is sometime used as a rapid, quality control test for a variety of food products, rather than the more time-consuming microfluorometric method (AOAC Method 984.26). The procedure outlined below is from AOAC Method 967.21.