Acidic deep eutectic solvent as a greener medium for highly efficient extraction of anthocyanins from blackberry fruit: Optimization, stability and purification with two-aqueous phase method

Abstract

Natural deep eutectic solvents (NADESs) are a sustainable and green solution for the recovery of food ingredients such as pigments. In this work, the extraction conditions to obtain the maximum anthocyanins from blackberry fruit were investigated using NADES composed of choline chloride-acetic acid (CHAC) as the green solvent. The central composite design was used conseidering molar ratio, water content, solvent ratio and extraction time as independent variables and total anthocyanin content (TAC), cyanidin-3-glucoside, cyanidin-3-rutinoside, pelargonidin-3-glucoside and cyanidin chloride as responses. The results showed that the independent variables significantly affected the responses. The optimum conditions for CHAC were 1:3.5 M, 40 %, 30 g and 15 min for molar ratio, water content, solvent ratio and extraction time, respectively. Under these conditions, the experimental responses were 131.54 ± 7.89 mg CGE/100 g, 1208.08 ± 13.76 mg/kg, 163.43 ± 1.72 mg/kg, 53.78 ± 1.37 mg/kg and 91.98 ± 0.62 mg/kg for TAC, cyanidin-3-glucoside, cyanidin-3-rutinoside, pelargonidin-3-glucoside and cyanidin chloride, respectively. The pH, viscosity and electric conductivity of CHAC were determined as 1.24 ± 0.03, 1.21 ± 0.17 and 7.50 ± 0.55 mPa and 4675.33 ± 57.74 µS.cm−1, respectively. After storing the NADES extract for 28 days in the dark, cyanidin-3-glucoside, cyanidin-3-rutinoside, pelargonidin-3-glucoside and cyanidin chloride remained 71.57 ± 0.64 %, 75.00 ± 0.26 %, 33.42 ± 0.41 % and 71.45 ± 0.21 %, respectively. Over the 28-day exposure of the NADES extract to light, the cyanidin-3-glucoside, cyanidin-3-rutinoside, pelargonidin-3-glucoside and cyanidin chloride remained 19.09 ± 0.10 %, 34.89 ± 2.28, 13.28 ± 0.25 and 30.97 ± 1.10, respectively. The application of the aqueous two-phase system resulted in the preliminary purification of the NADES extract, providing the highest purity in the top phase for cyanidin-3-glucoside (68.85 ± 1.05 %). The findings revealed that CHAC is a promising green medium for the industrial extraction of anthocyanins, and the aqueous two-phase is suitable for the purification of the anthocyanin-rich extract obtained with NADES.