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

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…