In general, vegetables are an excellent source of vitamins and minerals to our diet, since most vegetables are rich in vitamins, especially vitamin A and C. Vegetables contain lots of vitamin A of carrots for example, while vegetables that contain lots of vitamin C, for example tomato. Other types of vitamins contained in vegetables is vitamin B1 (thiamin), and minerals such as calcium (Ca) and iron (Fe).
Vitamin and mineral content of some vegetables can be seen in Table 6. Vitamin has the characteristics unstable or prone to change. Vitamin C for example, is easily oxidized or easily corrupted by the influence of light and high temperatures. Changes of vitamin C in the form of a percentage loss of vitamin C by a temperature effect can be seen in Table 7.
Table 6. Vitamin and mineral several kinds of vegetables
Source: Nutrition Directorate of the Ministry of Health (1972)
Table 7. Loss of vitamin C in vegetables in storage
*) Harris, Von Loesecke (1960) in the Tien et al (1992)
Vitamin C (ascorbic acid) is usually in the form of reduced and oxidized as dehydroascorbic acid together. In alkaline conditions and pH neutral, acid hydrolysis dehidroaskorbat experience diketogulonat acid forming. Diketogulonat acid form does not have activity as vitamin C, and materials will be brown due to the Maillard reaction.