Ultrasound treatment degrades, changes the color, and improves the antioxidant activity of the anthocyanins in red radish
Wenfeng Li, Pengling Gong, Hongming Ma, Rong Xie, Jiangqin Wei, Mengyi Xu
Abstract
Ultrasonic technology is commonly used to extract anthocyanins from food. This study extracted anthocyanins from red radish (ARR), which were purified using AB-8 macroporous resin. UHPLC-QQQ-MS/MS analysis identified 25 anthocyanins in the ARR, of which pelargonidin-3-(feruloyl)diglucoside-5-(malonyl)glucoside (P3FD5MG), pelargonidin-3-(p-coumaroyl)diglucoside-5-(malonyl)glucoside (P3PD5MG), and pelargonidin-3-(caffeoyl)diglucoside-5-(malonyl)glucoside (P3CD5MG) were the most abundant. Ultrasound treatment at 136–358 W for 120 min decreased the contents of P3FD5MG, P3PD5MG, and P3CD5MG by 19.5%–34.7%, 18.9%–42.7%, and 21.5%–37.3%, respectively. The degradation of P3FD5MG, P3PD5MG, and P3CD5MG increased by applying ultrasound treatment for an extended period and higher power, following a second-order kinetic equation. The degradation process during ultrasound treatment produced p-hydroxybenzoic acid (PHBA) and protocatechuic acid (PA), improving the ferric reducing antioxidant power (FRAP) and 1,1-diphenyl-2-picrylhydrazyl radical (DPPH·) scavenging activity of ARR. Moreover, ultrasound treatment caused degradation of anthocyanins, thereby leading to distinct color changes in the ARR. Therefore, ultrasound treatment should be used cautiously when processing red radish to preserve their color.