Individual and synergistic effect of multi-frequency ultrasound and electro-infrared pretreatments on polyphenol accumulation and drying characteristics of edible roses

[Display omitted] •Edible roses treated by 20/40/60 kHz ultrasound accumulated the highest polyphenols.•19 phenolic compounds were identified from rose extract by UPLC-qTOF-MS/MS.•Ultrasonic treatment changed microstructure and equivalent circuit parameters of rose.•Electro-infrared treatment inactivated polyphenol oxidase effectively.•Ultrasound-infrared treatment improved drying efficiency and quality attributes of VFD rose. The freeze-dried (FD) edible roses with high content of bioactive substances and superior flavor have been favored by consumers. Nevertheless, the development of freeze-dried rose industry has been plagued by a long drying time and low efficiency. This study investigated the effects of ultrasonic pretreatment (UP) in multi-frequency modes and electro-infrared pretreatment (EIP) prior to FD on polyphenol accumulation and drying characteristics of roses. The mechanism was explored by the changes in microstructure, equivalent circuit parameters, and phenol identifications of rose. The results showed that the FD time of roses decreased by 26 % after ultrasonic-infrared sequential synergistic pretreatment (UP + EIP) due to the damage of cell membrane permeability from UP. The quality attributes of UP + EIP products including color, phenols, and antioxidant activity (DPPH and ABTS radical scavenging rates) remarkably improved. UP + EIP significantly (p