Comparison between ultra-homogenisation and ultrasound for extraction of phenolic compounds from teff (Eragrostis tef (Zucc.))

This study investigated the effect of the solvent composition on the extraction of phenolic compounds from teff grains and compared the efficiency between the techniques homogeniser-assisted extraction (HAE) and ultrasound-assisted extraction (UAE). The solvents used were water, ethanol and methanol, and the response analysed was the total phenolic content (TPC). The quantitative profile of polyphenols extracted was also determined by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-TQD). According to the optimisation, the maximum response was estimated at solvent ratios of 51:40:9 and 49:26:25 (water/ethanol/methanol, v/v/v) for HAE and UAE, respectively. Under optimal conditions, the extraction technique did not significantly influence the TPC extracted, but the TFC (total flavonoid content) and the antioxidant capacity were significantly higher when UAE was used. The phenolic acids p-coumaric and protocatechuic and the flavonoids quercetin, rutin and myricetin were the main polyphenols extracted. Both techniques studied were efficient in extracting polyphenols from whole teff grains.