LAUSR

Response surface methodology was applied to investigate the influence of powder content (powder-to-solvent ratio), extraction time and extraction temperature on ethanolic extraction of ginger antioxidants. The use of colour and absorbance properties of the ginger extract for rapid estimation of its antioxidant properties was also investigated. The results indicate that ethanolic extraction of ginger could give rise to 239% (6272 ± 1 mg catechin equivalent per litre) and 269% (701.5 ± 1 mg gallic acid equivalent per litre) increases in extracted total flavonoids and total phenols contents, respectively, when compared to aqueous extraction, under single response optimisation conditions. The extraction of total flavonoids was significantly influenced (p < 0.05) by the powder content only. The extraction of polyphenols was significantly influenced by extraction temperature, extraction time and powder content. The ethanolic extraction of ginger total phenols was maximised at temperature of 36.3 °C and time of 36.1 min. Reduction in total phenols content values were observed as extraction temperatures and times moved closer to 70 °C and 90 min, respectively, thus suggesting degradation of some ginger phenolics at longer extraction times and higher extraction temperatures. The absorbance at 510 nm and a* (red-green balance) of the ethanolic ginger extract were linked to the total flavonoids content and the total phenols content of the extract, respectively.