Evaluation of valuable nutrients in selected genotypes of marula (Sclerocarya birrea ssp. caffra)

Different marula clones domesticated in the arid Negev desert were evaluated for their horticultural behavior physiological and antioxidant characteristics of their fruits. Two types of abscission pattern were detected, early and late. Fruit yields fluctuated from year to year (6-45 kg/tree) with large differences between clones (few fruits to 45 kg/tree). The clones also differed in fruit weight (34.41 ± 0.91 to 56.74 ± 1.65 g), shape, and juice content. Ascorbic acid content was found to be high in all the clones with significant differences among clones and time post-abscission. Clone no 12 at 1 week post-abscission had the higher ascorbic acid content, 21.177 mg/g dry weight and clone no 4 at the abscission day had the lower ascorbic acid content, 7.142 mg ascorbic acid/g dry weight. The total antioxidant and polyphenol content of the juice varied among clones and with time post-abscission, as did the activity of superoxide dismutase (about 1.40 IU/g dry weight of SOD at week 0 for all clones, to 2.67 IU/g dry weight at the third week post-abscission). Fresh marula juice had, on average, four times more antioxidant than the juice of either orange or pomegranate (marula ascorbic acid equivalent: 8.52 ± 0.76 mM to 23.26 ± 2.20 mM versus 2.72 ± 0.39 mM to 7.38 ± 0.18 mM and 2.56 ± 0.41 mM to 3.92 ± 0.18 mM, respectively), considered to be rich in antioxidants. Marula ice cream and jam manufactured according to industrial protocols were rich in ascorbic acid 45 days post-production. In conclusion, selected genotypes of marula exhibited superior horticultural traits and high antioxidant contents. These data should be of value in selecting marula clones for commercial planting.