Abstract:
The indigenous root and tuber crops in Sri Lanka have not been exploited by the food industry.
With a view to establish their nutritional importance and promote consumption and industry usage,
this study determined the contents of selected bio active compounds and antioxidant properties in
15 root and tuber crops varieties namely, Amorphophallus paeoniifolius, Canna indica (2
Selections), Dioscorea alata (6 varieties), D. bulbifera, D. esculenta, Maranta arundinacea and
Xanthosoma sagittifolium (3 varieties), both in their raw and processed (boiled) forms. Antioxidant
capacity (AOC) of yams was determined by Ferric Reducing Antioxidant Power (FRAP) Assay and
2,2-diphenyl-1-picrylhydrazyl (DPPH) Radical Scavenging Assay. Total phenolics (TPC) and
ascorbic acid contents (AAC) were determined by Folin-Ciocalteu method and 2,6-dichlorophenol
indophenol visual titration method, respectively. Chemical analyses were performed on triplicate
samples. The AOC in the raw form ranged from 56 mg TE/g dry weight (D. bulbifera) to 30 mg
TE/g dry weight (M. arundinaceae) while it showed a 0.4% (D. alata ‘Raja ala’) to 45% (D. alata ‘Hingurala’) decrease when boiled. The TPC in the raw form was highest in D. bulbifera (190.5
GAE; mg/100 g) while it was lowest in D. esculenta (6 mg/100 g). Dioscorea alata ‘Jaffna
Rasawalli’ showed the highest loss (95%) of phenolics when subjected to boiling. The Xanthosoma
sagittifolium varieties ‘Kiri ala’ and ‘Isuru’ had the highest AAC (12 mg/100 mg) in raw form while it
was lowest (2 mg/100 mg) in M. arundinaceae. D. bulbifera and X. sagittifolium ‘Kaha kiri ala’
retained relatively higher levels of antioxidants in their boiled forms. The contents of bioactive
compounds in yams tended to decrease when subject to boiling. However, the degree of loss
depended on the yam variety. Further research should focus on developing processing
technologies to minimize the loss of bioactive compounds in root and tuber crops.
