Quantification of Antioxidant Capacity and Content of Two Blackberry Cultivars Grown In Oklahoma

Blackberry (Rubus sp.) is a good source of antioxidants and contains high amount of phenolic compounds, mainly anthocyanins. Anthocyanins, a part of the flavonoid family, are common pigments in many berry fruits and have been studied for their health benefits. Two blackberry cultivars (Apache and Ouachita) that are commonly grown in the Midwest were harvested from two locations, one in Oklahoma and one in Arkansas. Assays were conducted to determine total phenolics and anthocyanin contents. Oxygen Radical Absorbance Capacity (ORAC) assays were also conducted in order to measure antioxidant activity. All of the blackberries were collected during summer, 2008 and stored at about -5 °C prior to analysis.  The berries were processed and samples were taken for further analysis at three different stages: whole berries, juice, and wine. Whole berries were extracted using 40 % acetone, 40 % methanol, 20 % deionized water and 0.1 % acetic acid prior to analysis; juice and wine were analyzed without further extraction. Folin-ciocalteu method was used to measure total phenolic contents and the pH differential method was conducted to evaluate anthocyanin contents. ORAC assays were performed using a fluorescein probe with sample incubation at 37°C, an excitation frequency of 485 nm, and an emission frequency of 535 nm. Correlations were observed between total phenolic contents, anthocyanin contents and ORAC assays. Blackberry extract had the highest amount of total phenolics, anthocyanins, and ORAC followed by juice and wine samples. Overall, Apache berries had higher concentrations of phenolics, anthocyanins and higher ORAC values than Ouachita. For both cultivars, blackberries from Arkansas had lower concentrations of phenolics and anthocyanins as well as lower ORAC values than blackberries grown in Oklahoma.