Abstract
The effects of extraction temperature, time and concentration (powder to solvent ratio) on extraction of flavonoids and polyphenols from tea using aqueous, aqueous ethanolic and absolute ethanolic solvents were investigated using response surface methodology. Concentration had the most significant influence on the extraction of the tea antioxidants. For both the aqueous and absolute ethanolic solvents, the extraction of polyphenols and flavonoids was maximised at temperatures close to the highest extraction temperatures investigated. Aqueous extraction of flavonoids and polyphenols was optimised at 92.01 °C and 95.75 °C, respectively and the absolute ethanolic extraction was optimised at 69.50 °C and 70.00 °C, respectively. A comparison of the three extraction solvents based on the single response optimisation approach indicated that aqueous extraction gave extract with highest total flavonoids (26,697.2 mg CE/L) content while aqueous ethanolic extraction gave extract with the highest total phenols content (4068.76 mg GAE/L). The study also suggests that pH, hue index and absorbance of extracts at 510 and 610 nm could be used for developing rapid prediction protocols for tea polyphenols and flavonoids.
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