Extraction and separation of anthocyanins from Kushui rose by ethanol-(NH₄)₂SO₄ aqueous two-phase system

Simultaneous extraction of anthocyanins and removal of sugars from Kushui rose was performed using an ethanol-ammonium sulphate aqueous two-phase system (ATPS). The effects of different parameters, such as type of salt, concentrations of salt and ethanol, temperature and pH on the partition coefficient and recovery of anthocyanins in the top system and sugars in the bottom system were studied. Furthermore, an experimental design of a three-level three-factor Box-Behnken design response surface methodology (RSM) was used to obtain optimal extraction conditions. The maximum partition coefficient (5.64) and recovery (78%) of anthocyanins in the top system within the investigated range were obtained at 22% (w/w) concentration of ammonium sulphate, 25% (w/w) concentration of ethanol, pH 5 and 33.5 °C. During the discussion of the main factors, the maximum recovery of sugars reached 70.09%. The HPLC profile of anthocyanins obtained from the ATPS top phase was similar to that of anthocyanins extracted by ethanol, which indicated that the ethanol-ammonium sulphate ATPS was suitable for the extraction of anthocyanins. On the basis of the anthocyanin stability experiment, anthocyanins extracted from Kushui rose should be stored at low pH and temperature.