Nutritional quality and bioactive constituents of six Australian plum varieties

While plums are widely touted for their health benefits, there is little data available on the levels of beneficial anthocyanins and other antioxidative compounds found in commercial Australian plums. As such, this study aims to provide context data on the typical levels and variation in plums available to consumers. Six commercial plum varieties were sourced from Central Queensland grocery stores, including two varieties developed and grown exclusively in Australia – Croc Egg and “King Midas” yellow plums – as well as four varieties grown both in Australia and internationally: black, Dapple Dandy, red and sugar plums. These were analyzed for antioxidants, phenolics, anthocyanins and mineral contents. Significant differences between varieties were observed in the levels of total phenolics (65–160 mg gallic acid equivalents 100 g−1 on a fresh weight basis), antioxidants (cupric reducing antioxidant potential of 174–542 mg Trolox equivalents 100 g−1) and anthocyanins (0.3–21.5 mg cyanidin-3-glucoside equivalents 100 g−1), as well as in the flavonols quercetin (0.02–0.15 mg 100 g−1) and quercetin-3-glucoside (0.21–2.87 mg 100 g−1). Mid-infrared attenuated total reflectance (MIR-ATR) spectroscopy combined with principal component analysis could separate varieties based on their phytochemical composition. The findings suggest that commercially available Australian plums contain similar levels of health-benefitting compounds to those found internationally, although the levels of these compounds depend strongly on the considered variety.