Effect of vacuum combined with ultrasound on color protection of pomegranate juice

Abstract Pomegranate juice is prone to color fission during processing and storage due to the instability of anthocyanins, resulting in significant economic losses. This study aims to inhibit the browning of pomegranate juice during processing using the combined technology of vacuum and ultrasound for maintaining its color as much as possible. Pomegranate juice was treated with vacuum (0.5 MPa) and ultrasound (300, 600, 900, 1200, and 1500 W; 15, 20, 25, 30, and 35 min), respectively, to investigate the effects on the color, antioxidant capacity, anthocyanin/polyphenol content, and polyphenol oxidase activity of pomegranate juice. The results showed that the combined treatment of vacuum and ultrasound had a better effect on improving the total anthocyanin content of pomegranate juice than vacuum or ultrasound treatment alone. Vacuum combined with ultrasound can reduce the browning during pomegranate juice processing, increasing browning inhibition rates by 46.01% and 46.19%; reduce the activity of PPO enzyme and increase the inhibition rate of PPO enzyme activity by 35.58%; maintain a high total phenolic content, increasing the total phenolic content of pomegranate juice by 29.27% and 33.79%, respectively; and improve the ABTS scavenging rates by 2.89% and 1.92%, and increase DPPH scavenging rates by 1.35% and 3.01%. Moreover, vacuum ultrasound treatment had no significant effect on the odor of pomegranate juice. Vacuum combined with ultrasonic treatment is beneficial for protecting the color of pomegranate juice and improving its antioxidant performance during the processing. Therefore, combined technology of vacuum and ultrasound would be a promising method for future food processing. Practical applications This study provides a simple and novel method for protecting the color of pomegranate juice during processing. The combination of vacuum and ultrasound has a certain protective effect on the color of pomegranate juice during processing, and also provides new ideas for color protection research.