Title : Effect of extraction temperature on the antioxidant activity of aqueous extracts from lotus root and white radish
Abstract:
Antioxidants' anti-inflammatory and anti-ageing effects on our bodies provide several health benefits. However, the human body naturally produces only a small concentration of antioxidants, requiring us to rely heavily on external sources. White radish (Raphanus sativus var. Longipinnatus) and lotus root (Nelumbo nucifera) are known as rich sources of antioxidants. Despite their popularity, optimum temperatures to maximise antioxidant extraction from simmering, a common cooking method, are understudied. This work details how antioxidant activities in aqueous solutions from the two vegetables at different extraction temperatures (0℃,25℃,50℃,75℃,100℃) were measured. Mixtures of standardised mass-to-volume ratios of shaved vegetables and distilled water were made, then left at respective temperatures for 1 hour. 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and Folin-Ciocalteu assay were then performed to quantify antioxidant activities through the inhibition rate (%) and total phenol contents, respectively. In both white radish and lotus root extracts, the antioxidant activities increased with rising temperature. The optimal temperature for antioxidant activity in white radish extract was at 50℃, while optimal antioxidant activity was at 100℃ in lotus root extracts. Past the peak temperatures, a decrease in antioxidant activities was observed, likely due to thermal degradation of antioxidants. The difference in the optimal temperatures results from the lower thermal stability of antioxidants in white radish compared to the antioxidants in the lotus roots. Overall, this work demonstrated potential application in households to obtain antioxidants from an everyday diet efficiently.
