Abstract
The present study evaluated the effect of boiling on the antioxidant capacity of Dioscorea alata (raja ala) using water extracts; raw yam extract, boiled yam extract prepared with water used in boiling, boiled yam extract prepared with fresh water. The total antioxidant capacity was measured by ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and reducing power assays. The total phenol, total flavonoid, monomeric anthocyanin and condensed tannin contents were measured by Folin-Ciocalteu, aluminium chloride, pH differential and vanillin assays respectively. The results indicated that FRAP, reducing power, total phenol and monomeric anthocyanin contents of the boiled yam extract prepared with fresh water were significantly lower (p Tropical Agricultural Research Vol. 26 (1): 109 – 119 (2014)
Highlights
Emerging research evidences regarding the impact of diet on human health beyond the basic nutrition has led to the curiosity among consumers
The total antioxidant capacity (TAC) of 3.89±0.86 μmol/g FW in boiled yam extract prepared with fresh water was significantly lower (p < 0.05) compared to treatment A and B
In the boiled yam extract prepared with fresh water, total phenol, total flavonoid and condensed tannin compounds had strong relationship with TAC measured by DPPH radical scavenging and reducing power assays, while ferric reducing antioxidant power (FRAP) had a weak correlation
Summary
Emerging research evidences regarding the impact of diet on human health beyond the basic nutrition has led to the curiosity among consumers. Antioxidants are believed to provide a number of health benefits such as, cancer prevention, cardio protection and enhancement of neurological function (Potter, 1997). An antioxidant is a molecule that inhibits the oxidation of other molecules. The mode of action of these compounds in disease prevention is believed to be suppression of oxidative stress. The edible tubers of genus Dioscorea are consumed in Sri Lanka as a source of energy for long time. Apart from the food value, D. alata (raja ala) cultivars were found to have health benefits such as immune stimulation (Shang et al, 2007) and antihypertensive effects (Liu et al, 2009). Raja ala is one of the most popular D. alata cultivars in Sri Lanka
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