Effect of Saccharomyces cerevisiae – Induced Fermentation on the Antioxidant Property of Roselle Calyx Aqueous Extract

This study investigated the effects of Saccharomyces cerevisiae-induced fermentation on the antioxidant properties of Roselle calyx aqueous extract and determined the physicochemical changes of the fermented extract. Total phenolics, total flavonoid, ascorbic acid content, total monomeric anthocyanin content and DPPH radical scavenging activity of roselle aqueous extract were investigated before and after fermentation. Roselle calyx aqueous extract was fermented for period of 10 days. During fermentation, the extract was evaluated for pH, alcohol (%), titratable acidity (%) and total soluble solids (oBrix). Total soluble solids and pH significantly decreased at the end of the fermentation whereas titratable acidity and alcohol content significantly increased. Fermentation caused significant reduction in total monomeric anthocyanin content from an initial value of 3518±30.8 to 1075±28.2 CGE/100 g dry extract whereas significant increase was observed in total phenolic content from 195.75±76.01 to 455.5±1.41 mgGAE/100 g dry extract and ascorbic acid content from 1392±101 to 2028±108 mg AAE/100 g dry extract and total flavonoids increased from 193.0±74.25 to 291.5±4.95 mgQE/100 g dry extract but it was not significant. There was also a significant increase in 1-1-diphenyl-2-picryl hydrazyl (DPPH) scavenging activity of roselle calyx aqueous extract from an initial value of 44.15% to final value of 71.10% after fermentation, leading to an increase in antioxidant activity. Therefore, the quantity of phenolic compounds increased with fermentation process. This study showed that roselle calyx aqueous extract fermented by Saccharomyces cerevisiae has a better antioxidant activity.