Ultrasound treatment inhibits browning and improves antioxidant capacity of fresh-cut sweet potato during cold storage

Controlling browning and mitigating oxidative damage are important factors when attempting to extend the shelf-life and high-quality features of fresh-cut sweet potato (Ipomoea batatas (L.) Lam). In order to preserve the color and antioxidant capacity, ultrasound (US) treatment at 40 kHz for 10 min was applied to investigate the effect on enzymatic browning of sweet potato slices. Changes in color, total phenolic content, total antioxidant capacity, phenol metabolism-related enzymes including phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), peroxidase (POD) were examined. Also investigated here were superoxide radical (O2−˙) and hydrogen peroxide (H2O2) contents, antioxidant enzymes including superoxide dismutase (SOD) and catalase (CAT) involved in reactive oxygen species metabolism. After storage lasting 10 days at 4 °C, US-treated slices maintained significantly (p < 0.05) higher luminosity (p = 0.000003) and chroma (p = 0.000018) by reducing PPO and POD activities, when compared to the control. Meanwhile, the induction of PAL was observed to positively correlate with higher total phenolic content (r = 0.818, p < 0.01; p = 6.1752 × 10−9), thereby enhancing antioxidant capacity to combat oxidative damage. Moreover, O2−˙ (p = 3.8046 × 10−10) and H2O2 (p = 0.000013) concentrations were significantly (p < 0.05) suppressed by activating CAT and SOD activities. Results suggested that US treatment could inhibit browning of fresh-cut sweet potato by reducing the activity of PPO and POD while improving total antioxidant capacity.