Vitamin C performs many functions in the human body and is very important for its proper functioning. The main vitamin C sources in the human diet are fruits and vegetables. Changes of total content of vitamin C (Tc), L-ascorbic acid (AA) and dehydro-L-ascorbic acid (DHA) in selected fruits and vegetables during storage at 20°C until spoilage were determined. A decrease of Tc and AA contents and an increase of DHA concentration were noted. Products of high acidity such as lemon and tomato were characterized by the highest retention of vitamin C. An increase of the DHA to Tc ratio (%) was observed. On the first day of storage the DHA/Tc ratio was higher than 10% in broccoli, cucumber and banana, while on the last day – it amounted over 40% in banana and cucumber, between 20 and 40% in parsley leaves and broccoli, and below 20% in tomato, cauliflower and lemon. In order to obtain correct results of vitamin C determination in fruits and vegetables it is necessary to take DHA content into consideration.

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