Fruit and vegetable consumption has been associated with decreased mortality and lowers the incidence of cancer (Dragsted et al., 1993) and cardiovascular disease (Verlangieri et al., 1985). Fruits contain several different families of phytochemicals, which are thought to contribute to this decreased risk. Antioxidant capacity is one measure of phytochemical content. Those compounds responsible for most of a fruit's antioxidant capacity are phenolic acids, anthocyanins, and other flavonoids (Cao et al., 1997). Antioxidant capacity, anthocyanin content, and total phenolic content are highest when a fruit is ripe (Wang and Lin, 2000). Ripe raspberries have a high antioxidant capacity and total phenolic content compared with most other berries and are a good source of ellagic acid, an antioxidant with powerful antimicrobial properties against many human pathogens (De Ancos et al., 2000; Heinonen, 2007).
Most recent raspberry research has focused on raspberries that were grown in Finland, Spain, or the northeastern or midwestern United States (Anttonen and Karjalainen, 2005; De Ancos et al., 2000; González et al., 2003; Kähkönen et al., 2001; Liu et al., 2002; Ozgen et al., 2008). Although not discussed by any of the cited authors, most temperate environment raspberries are harvested in the spring from floricane (second year spring-bearing) plants. Most of the raspberries grown in hot, dry conditions are harvested in the fall from primocane (first year bearing) plants that have been nourished from irrigation and fertilization throughout the summer. The dry climate results in berries that can lose moisture more quickly but are otherwise similar to raspberries grown in other climates (Cornaby Farms, personal communication). Particularly late in the season, as the weather begins to turn cold (but still dry), some cultivars produce significantly smaller, darker berries, whereas other cultivars do not. Primocane dry climate raspberry research is underrepresented in the literature.
Cultivar, berry ripeness, growing conditions, length of storage, and processing methods result in differences in antioxidant activity and phenolic content of raspberries (Ozgen et al., 2008). Previously published data (Anttonen and Karjalainen, 2005; De Ancos et al., 2000; González et al., 2003; Kähkönen et al., 2001; Liu et al., 2002; Ozgen et al., 2008) has limited application to dry condition raspberry farming. The objective of this study was to measure antioxidant capacity and total phenolic content of six cultivars of primocane raspberries grown under controlled fertigation (fertilizer provided to the plant through irrigation water) in Utah. It was hypothesized that antioxidant capacity and phenolic content would vary across cultivar, across the season, and between storage treatments.
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