Optimization of ellagic acid extraction from blueberry pulp through enzymatic hydrolysis combined with ultrasound-assisted organic solvent

The aim of this study was to optimize the technology used to extract ellagic acid from blueberry pomace. For single factor analysis, an enzymatic hydrolysis test showed that temperature, pH value and liquid-to-material ratio exhibited significant effects on ellagic acid content, as did three factors (the liquid-to-material ratio, ultrasonication time and temperature) for the ultrasound-assisted organic solvent method. A Box–Behnken design was applied for the enzymatic hydrolysis test and the ultrasound-assisted organic solvent method to determine the optimal combination scheme. For enzymatic hydrolysis, this scheme was 7:1 for the liquid-to-material ratio, 46 °C for the temperature of enzymatic hydrolysis and 4.9 for the pH value; under these conditions, an ellagic acid content of 1.96 mg/g (FW) was obtained. The optimal combination scheme for the ultrasound-assisted organic solvent was 2:1 for the liquid-to-material ratio, 65 °C for ultrasonication temperature and 82 min for the ultrasonication time, which produced ellagic acid contents of 7.92 mg/g (FW) and an extraction yield of 32.41%, respectively. The content and yield of ellagic acid in the extraction from blueberry pomace were greatly increased by combining enzymatic hydrolysis and an ultrasound-assisted organic solvent method. This study provides a theoretical reference for utilizing and developing blueberry pomace.