Study of anthocyanins as related to stability of infrared freeze-dried rose flower using novel ultrasound pretreatment

Abstract

The present study was undertaken to determine the mechanism of anthocyanin content (ACNs) and related stability of infrared freeze-dried rose flowers using novel ultrasound pretreatments (20 kHz and 45 kHz for 5, 10 and 15 min). Additionally, the impact of such processing on peroxidase, polyphenol oxidase, color, moisture, total phenolic, total flavonoid, anthocyanins degradation during storage and chemical structure of infrared freeze-dried flowers was evaluated quantitatively. Peroxidase in rose flowers was effectively inactivated while polyphenol oxidase was activated very slowly (85, 95.67, 87.33, 77.67, 93, 98, 90.67%) by ultrasound pretreatment at 45 kHz and 20 kHz for 5, 10 and 15 min, respectively. The TPC and TFC of dried rose flowers pretreated by 45 kHz ultrasound (US) was also higher than that of dried roses pretreated by 20 kHz US. Moreover, US at 45 kHz was beneficial for the retention of color and anthocyanins of roses after infrared freeze-drying. In addition, US treatment at 45 kHz for 10 min resulted the lowest ACNs degradation rate during storage. These results demonstrate that US treatment at 45 kHz is a potential technique for improving the stability of anthocyanins during its processing and storage.