Alternation of secondary metabolites and quality attributes in Valencia Orange fruit ( Citrus sinensis ) as influenced by storage period and edible covers.

Flavonoids (FGs) are a large group of polyphenolic compounds with low molecular weight, found in free and glycozidic forms in plants. Citrus fruits can be used as a food supplement containing hesperidin and flavonoids to prevent infections and boost the immune system in human body. The aim of this study was the investigation of the effect of clove oil and storage period on the amount of hesperidin and naringin component in orange peel (cv. Valencia). Four treatments including clove oil (1 %), wax, mixture of wax-clove oil, control and storage period were applied. Treated fruits were stored at 7 °C and 85 % relative humidity for 3 months and naringin, hesperidin, antioxidant activity, total pheenolic compounds, TSS, Vitamin C, fruits weight loss, pH, acidity and carbohydrates content were measured every 3 weeks. The amount of hesperidin and naringin was determined using high performance liquid chromatography at the detection wavelength of 285 nm. Antioxidant activity was measured using the 1, 1-diphenyl-2-picrylhydrazyl-hydrate (DPPH) free radical scavenging assay. Total phenolic compounds were measured using the Folin-Ciocalteu micro method. Results showed that naringin and hesperidin were decreased during storage. Different treatment only had significant effect on the amount of hesperidin while storage period affected both of narigin and hesperidin. Results of correlation study, indicated strong relation between antioxidant activity and amount of naringin and hesperidin during storage time. However, at the end of storage period, the amount of hesperidin and naringin were diminished independent of different covers. Probably anaerobic condition caused such reduction. Results showed that the amount of TSS, fruit hardness, weight loss, total sugar and fructose content were increased during storage period while total acidity, pH and glucose content showed descending trend during storage periods. In conclusion, hesperidin and naringin of peels can be used as suitable quality indexes indicating proper conditions for storage.