Recent interest in the human health-promoting properties of fruit phenolics, and especially fruit flavonoids, has stimulated research on how these secondary metabolites may be affected by pre- and postharvest horticultural factors. Resveratrol, although a minor phenolic in many fruit, possesses potent bioactivities, and is therefore of particular interest. To study the effects of postharvest storage and UV-C irradiation on selected phenolic components and antioxidant capacity of cranberry (Vaccinium macrocarpon), fruit of cv. Pilgrim, Stevens, and Bergman, were irradiated with UV-C at levels between 0 and 2.0 KJ·m-2, followed by storage at 9 °C for 7 and 17 d. Total phenolic content did not change during storage. However, resveratrol content was higher and antioxidant capacity (ORAC) was lower at 7 days of storage compared to 17 days. There was no main effect of UV-C on total phenolics, anthocyanins, resveratrol, or ORAC. However, there was an interaction between storage time and UV-C irradiation. Anthocyanin content was lower at 7 days, and higher at 17 days, at UV dosages of 1.0 or 2.0 KJ·m-2. Resveratrol content was higher in UV-C irradiated fruit at 7 days, while at 17 days there was no difference between UV-treated and untreated fruit.
The antioxidant properties of blueberries have been examined only in ripe fruit, although fruit of different maturities are used in processed food products. In this study, highbush blueberry cultivars Bergitta, Bluegold, and Nelson highbush blueberry fruit at different stages of ripeness were examined to characterize differences in oxygen radical absorbing capacity (ORAC) and the phenolic components responsible for ORAC. Underripe fruit at different stages of maturity were also stored at 20 °C for up to 8 days to assess changes in ORAC and phenolic content. Anthocyanin content was substantially higher in fruit of more advanced stages of ripeness. In contrast, the phenolic content and ORAC were lower in the riper fruit. Anthocyanins continued to form during storage, although rate of pigment formation declined after about 4 days. Less anthocyanin pigment was formed in the less ripe fruit. After 8 days of storage, the anthocyanin content of fruit harvested 5% to 50% or 50% to 95% blue exceeded that of ripe fruit. Up to 60% of the total phenolic content could be accounted for by anthocyanins. ORAC was positively correlated with total phenolic content (R2 = 0.78), but not with anthocyanin content.