Multi-Frequency Ultrasonic Extraction of Anthocyanins from Blueberry Pomace and Evaluation of Its Antioxidant Activity
Aijun Hu, Shu-Ting Hao, Jie Zheng, Lin Chen, Peng-peng Sun
Abstract
BACKGROUND: A large amount of blueberry pomace is discarded and wasted. OBJECTIVE: To make full use of blueberry pomace and extract anthocyanins. METHOD: Multi-frequency ultrasound was used to extract anthocyanins from blueberry pomace. The effects of different extraction conditions on the anthocyanin yields were studied. The antioxidant activity of anthocyanins was evaluated, and the main anthocyanin components were identified by HPLC-electrospray ionization (ESI)-MS/MS. RESULTS: The optimal anthocyanin extraction conditions were as follows: dual-frequency ultrasound of 40 + 80 kHz, ultrasonic power of 350 W, extraction temperature of 50°C, and extraction time of 40 min. Compared with single frequency (25 kHz) and tri-frequency ultrasound (25 + 40 + 80 kHz), the anthocyanin yield with dual-frequency ultrasound increased by 15.26% and 5.45% respectively. Furthermore, the antioxidant activities (DPPH, hydroxyl radical scavenging ability, and reducing power) of anthocyanins extracted with dual-frequency ultrasound were all higher than those without ultrasound. Seven kinds of anthocyanins were identified by HPLC-ESI-MS/MS. CONCLUSIONS: Dual-frequency ultrasound had a higher extraction yield than single frequency ultrasound, tri-frequency ultrasound, and no ultrasound. HIGHLIGHTS: Dual-frequency ultrasonic technology provides an effective approach for improving the extraction yield of anthocyanins from blueberry pomace.