Abstract

This study was aimed at evaluating the nutritional and antioxidant properties of raw and boiled tubers of Dioscorea dumetorum and D. hirtiflora. Tubers of D. hirtiflora were characterized by higher total essential amino acids (9576 mg/100 g dry weight (dw)) than those of D. dumetorum (1085 mg/100 g dw). Boiling decreased the total amino acid content of both tubers. Monounsaturated Fatty Acids (MUSFAs) and Polyunsaturated Fatty Acids (PUFAs) accounted for 15.92 and 26.64% in D. dumetorum tubers respectively whereas, MUSFAs and PUFAs accounted for 29.62 and 24.11% in D. hirtiflora tubers respectively. Boiling increased the total unsaturated fatty acids from 42.56 to 56.81% in D. dumetorum tubers and decreased it from 53.73 to 49.08% in D. hirtiflora tubers. The total phenolic content of boiled D. hirtiflora tubers showed 4.5-fold gain which might explain partly the increase in their antioxidant capacity (IC₅₀ 22.35 mg/L in DPPH assay). Boiling did not change significantly the antioxidant activity of D. dumetorum tubers (IC₅₀ 74.13 mg/L in DPPH assay) although a significant decrease in total phenolic (60%) and vitamin C contents (56.7%) was observed. These results suggest that boiled tubers of D. dumetorum and D. hirtiflora can contribute significantly to human nutrition and health.

Keywords:

Antioxidant activity, essential amino acids, polyunsaturated fatty acids, total phenolics, vitamin C, yam,

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