Changes in flavonoids, ascorbic acid, polyphenol content and antioxidant activity in cold-stored 'Fortune' mandarin

Dietary recommendations for healthy eating include the consumption of fruit and fruit juice whose beneficial health effects are ascribed, in part, to ascorbic acid and polyphenolic compounds, some of which have antioxidant properties and whose intake has also been associated with a low risk of developing degenerative diseases, certain forms of cancer, cardiovascular and neurological diseases. In the present study we have analysed the changes in flavonoids, ascorbic acid, polyphenols and antioxidant activity in 'Fortune' mandarin juice during cold-storage. 'Fortune' mandarins were stored at 5 degrees C and 95% relative humidity (RH) for 3 months. A high-performance liquid chromatography (HPLC) separation with photo-diode array detector was used to determine and quantify flavonoids. Identification was based on retention time and UV spectra by comparison with commercial standards. The following flavonoids; hesperidin, narirutin and didymin were determined and quantified. Folin-Ciocalteau colorimetric method was used to determine the total phenols content whereas antioxidant capacity was assessed using the free radical DPPH center dot (1,1-diphenyl-2-picrylhydrazyl) and expressed as Trolox Equivalent Antioxidant Capacity (TEAC). Flavonoids, polyphenols content, ascorbic acid (AA) and total antioxidant activity remained unchanged during storage period. The correlation between TEAC values, AA and flavonoids content in fruits confirmed these compounds as the main antioxidants in citrus fruit.