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Title: Changes of flavonoid content and antioxidant capacity in blueberries after UV-C illumination

item Wang, Chien
item Wang, Shiow

Submitted to: Journal of Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2009
Publication Date: 6/7/2009
Citation: Wang, C.Y., Chen, C., Wang, S.Y. 2009. Changes of flavonoid content and antioxidant capacity in blueberries after UV-C illumination. Journal of Food Chemistry. 117:426-431.

Interpretive Summary: Decay of fruits and vegetables is one of the major causes of postharvest losses in fresh produce. Various methods have been used to inhibit decay. Most of these methods involve the use of fungicides. Increased resistance of many pathogens to fungicides and the concerns over health risks and environmental contamination have resulted in the withdrawal of a number of key fungicides from the market. These developments have stimulated the search for alternative methods of treatment. We have found that by using brief periods of UV-C exposure, better quality of blueberries could be maintained as compared to the control fruit. After 1, 5, 10 and 15 minutes of exposure of blueberries to germicidal UV-C lamps, higher antioxidant values were detected in the treated samples than in the untreated fruit. Thus, UV-C treatment is beneficial for maintaining the quality of blueberry fruit. Information presented in this study is of interested to other postharvest researchers and is useful to the produce industry.

Technical Abstract: The levels of flavonoids in blueberries were found to increase after illumination with UV-C. Phytochemicals affected included resveratrol, myricetin 3-arabinoside, quercetin 3-galactoside, quercetin derivative, kaempferol derivative, delphinidin-3-galactoside, cyaniding 3-galactoside, delphinidin 3-arabinoside, petunidin 3-galactoside, petunidin 3-glucoside, petunidin 3-arabinoside, malvidin 3-galactoside, malvidin-3-arabinoside, and chlorogenic acid as analyzed by HPLC. Significantly higher antioxidant capacity was detected in fruit treated with 2.15, 4.30, or 6.45 kJ m-2 compared to control fruit. UV-C dosage of 0.43 kJ m-2 also increased phenolics and anthocyanins, but to a lesser extent. The optimum doses of UV-C for enhancing phytochemical content in blueberries were 2.15 and 4.30 kJ m-2. These data suggest that proper use of UV-C illumination is capable of modifying the phytochemical content of blueberries, resulting in increased health benefits. Time course measurements of the effects of UV-C revealed that the strongest responses of fruit to UV-C treatment occurred instantly after the illumination and the effects diminished with time. Therefore, even though residual effects were evident following UV-C exposure, the best results were obtained immediately after the treatment.