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

The levels of flavonoids in blueberries (Vaccinium corymbosum L.) were found to increase after illumination with UV-C. Phytochemicals affected included resveratrol, myricetin-3-arabinoside, quercetin-3-galactoside, quercetin-3-glucoside, kaempferol-3-glucuronide, delphinidin-3-galactoside, cyanidin-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 the 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. 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.