Effect of ultrasound-assisted extraction combined with enzymatic pretreatment on bioactive compounds, antioxidant capacity and flavor characteristics of grape pulp extracts
Rongfang Li, Haiyan Zhu, Wenjie Du, Gaoheng Li, Yuzong Zhao, K . W . Song, Jun Qiu, Jinjin Liu, Song Fang
Abstract
To obtain grape pulp extracts with high quality, this study optimized the ultrasound-assisted extraction process using the response surface methodology, and further investigated the effect of solvent reflux extraction and ultrasound-assisted extraction with or without the enzymatic pretreatment on bioactive compounds, antioxidant capacity and flavor characteristics of grape pulp extracts. Results indicated that the optimal extraction conditions for ultrasound-assisted extracts of grape pulp (UAE) were 16 min ultrasonic time, 70 % ultrasonic amplitude, and 28 °C ultrasonic temperature, resulting in an extraction yield of 14.94 %, a total phenolic content of 14.38 mg GAE/ g, and a total flavonoid content of 2.98 mg RE/g. Moreover, grape pulp extracts prepared by ultrasound-assisted extraction combine with enzymatic pretreatment (UEAE) had highest bioactive compounds content and exhibited the best antioxidant capacity among the four grape extracts. There were significant differences in flavor among four grape extracts, and the aroma characteristics of UEAE were significantly improved in comparison to other grape extracts. Molecular docking revealed that the stable interactions of these aroma compounds and olfactory receptors were mainly attributed to hydrogen bonding and hydrophobic effects. These findings revealed that ultrasound-assisted extraction combined with enzymatic pretreatment not only enhanced the bioactive compounds content, but also remarkably improved the flavor characteristics of grape pulp extracts. This study offers valuable insights into the extraction and utilization of grape extracts.