Highbush blueberries Vaccinium corymbosum L., raspberries Rubus idaeus L. and black currants Ribes nigrum L. -: Influence of cultivar on antioxidant activity and other quality parameters

During the last years, research has been focussed on antioxidants in fruits and vegetables as important components in reducing chronic diseases such as cancer and cardiovascular disease (Steinmetz and Potter, 1996; Ness and Powles, 1997; Reddy and Katan, 2004; Blomhoff, 2005). Berry fruits were recently analysed in a Norwegian screening study, showing a high level of antioxidants in this type of fruits (Halvorsen et al., 2002). Different cultivars of red raspberries and black currants are widely grown and consumed in this country, while commercial highbush blueberry production started during the last decade. Fruits from highbush blueberry, red raspberry and black currant cultivars were used in the experiments to determine antioxidant activity. The plants were grown in the South-Eastern part of Norway (59 degrees 40'N). Highbush blueberry cultivars: 'Ama', 'Berkeley', 'Bluechip', 'Bluecrop', 'Bluejay', 'Bluetta', 'Duke', 'Earliblue', 'Goldtraube', 'Hardyblue', 'Heerma', 'Nui', 'Patriot', 'Puru', 'Putte', 'Reka', 'Spartan', 'Sunrise' and 'Toro'. Raspberry cultivars: 'Algonquin', 'Frosta', 'Glen Ample', 'Tambar', 'Tea', 'Tulameen' and 'Veten'. Black currant cultivars: 'Ben Alder', 'Ben Nevis', 'Ben Tirran', 'Ben Tron', 'Hedda', 'H (a) over circle kon' and 'Kristin'. To measure antioxidant activity the FRAP-method (Ferric Reducing Ability of Plasma) was used. In addition to antioxidant activity, fruit weight, optical density in the fruit juice and L-ascorbic acid, measured by HPLC, is shown. Results from the growing seasons 2002-2004 are presented. Berries were harvested in July to August all years at commercial stage of ripeness. Compared to other food products, as can be found in the literature, all the three berry species described, had a very high antioxidant activity, with values of 8.00 mmol/100g (black currants), 4.23 (red raspberries) and 3.88 for highbush blueberries. The results show that antioxidant activity was related to species, cultivar and berry size. Small-sized berry cultivars had higher values.