Optimization of Ultra-high Pressure Extraction and the Antioxidant Activity of Anthocyanins from Blueberry Pomace

The objective of this study was to optimize the ultra-high pressure extraction (UPE) process of anthocyanins extracted from blueberry pomace and to investigate the antioxidant activity of the anthocyanin extracts. In the present study, the extraction process of anthocyanins was optimized by single factor experiments and Box-Behnken response surface methodology, using blueberry pomace as raw extraction material. The DPPH free radical scavenging rate, hydroxyl radical scavenging rate, and FRAP iron ion reducing ability of the extracts were determined to evaluate the in vitro antioxidant activity of blueberry pomace anthocyanins, with vitamin C (V_C) used as a positive control. The components of anthocyanins extracted from blueberry pomace were analyzed by high performance liquid chromatography (HPLC). The optimum conditions of the anthocyanins extraction from blueberry pomac were as follows: extraction pressure at 400 MPa, extraction time for 9 min, 60% ethanol concentration, solid-liquidratio at 1:20 g/mL. Under these conditions, the extraction yield of blueberry pomace anthocyanins was 5.93±0.06 mg/g. Compared to conventional solvent extraction (CSE) and ultrasonic-assisted extraction (USE), ultra-high pressure-assisted extraction (UPE) had the better extraction effect, with the extraction yield of blueberry pomace anthocyanins increased 25.11% and 10.02%, respectively. Blueberry pomace anthocyanins had strong DPPH free radical scavenging effect, which was comparable to the same concentration of V_C (P>0.05). However, the hydroxyl radical scavenging activity and the FRAP iron ion reducing ability of blueberry pomace anthocyanins were significantly lower than those of V_C at the same concentration (P<0.05). The 13 peaks of the anthocyanin extracts from blueberry pomace were tentatively identied by HPLC analysis, among which the content of malvidin-3-galactoside was the highest. These results indicated that UPE was an efficient method for extracting blueberry pomace anthocyanins which have potential application value to be used as a functional food ingredient or nutraceutical due to their antioxidant activity.