Vitamin C
Vitamins are more vulnerable to heat destruction than are sugars and minerals. Pasteurization may cause low-level loss of some of these micronutrients. Vitamin C, also known as ascorbic acid, is the most vulnerable of the vitamins to heat degradation during pasteurization. Fresh-squeezed orange juice contains approximately 124 milligrams of vitamin C per cup; pasteurized orange juice contains approximately 84 milligrams, nearly one-third less. However, the amount of vitamin C in a single cup of pasteurized orange juice exceeds the recommended daily allowance for adults. Pasteurized grape and tomato juices are also good sources of vitamin C, with 63 milligrams and 45 milligrams per cup, respectively.
Other Vitamins
Thiamine may partially degrade during juice pasteurization. Although many pasteurized juices contain low levels of thiamine, fortified cereals and rice, whole-grain products, nuts and meats are the principal sources of this B-complex vitamin in the American diet. Other vitamins commonly found in popular fruit juices include B-6, E, niacin and riboflavin. The levels of these vitamins vary depending on the type of fruit juice and processing techniques.