Optimisation of extraction conditions for recovering carotenoids and antioxidant capacity from Gac peel using response surface methodology

The peel of Gac fruit is regarded as waste product in the processing of Gac although it contains high level of carotenoids and possesses a significant antioxidant capacity. This study optimised the extraction yields of carotenoids and antioxidant capacity from Gac peel. Different organic solvents were examined to determine the most suitable solvent for the extraction. The extraction conditions including time, temperature and solvent–solid ratio were then optimised for maximising extraction yields of carotenoids and antioxidant capacity from Gac peel using response surface methodology. Ethyl acetate was identified as the most suitable solvent. The optimal extraction time, temperature and solvent–solid ratio were 150 min, 40.7 °C and 80 mL g⁻¹, respectively. The carotenoid extraction yield and the antioxidant capacity extraction yield were 271 mg/100 g DW and 737 μm TE/100 g DW, respectively. Thus, the extraction using ethyl acetate with the ratio of 80:1 (mL solvent per g Gac peel) for 150 min at 40.7 °C is suggested for recovering carotenoids and antioxidant capacity from Gac peel.