Effects of ultrasonic pretreatment on far infrared vacuum drying properties and quality of Lycium barbarum / 中草药

ABSTRACT

Objective: To investigate the effect of ultrasonic technology on the far infrared vacuum drying process by using Lycium barbarum as the test material. Methods: The far-infrared vacuum drying test of L. barbarum was performed by ultrasonic technology. Using the independently developed far-infrared vacuum radiation drying equipment to study the far-infrared vacuum drying characteristics and quality change law of L. barbarum under different ultrasonic frequency, ultrasonic power and ultrasonic treatment time; And the Weibull function was used to simulate the drying process dynamically. Results: With the increase of ultrasonic frequency, ultrasonic power and ultrasonic treatment time, the drying time was significantly shortened, and the drying rate was significantly increased. The Weibull distribution function could better simulate the far-infrared vacuum drying process of L. barbarum under different ultrasonic treatment conditions (r2 = 0.993 9-0.999 2, χ2 = 0.000 1-0.000 6), the scale parameter α generally increased with the increase of ultrasonic frequency, ultrasonic power and ultrasonic processing time, and the shape parameter β was greater than 1; Compared with far-infrared vacuum dried products, ultrasonic treatment can not only reduce the loss of active ingredients of L. barbarum, but also shorten its drying time. Among them, the polysaccharides (812.846 mg/g) of the dried products obtained by the single factor test under the condition of 40 kHz ultrasonic frequency was the highest. When the ultrasonic power was 80 W, the total flavone content of L. barbarum after drying increased up to 28.69% in the single factor test. When the ultrasonic frequency was 60 kHz, the total phenol content of the dried L. barbarum products obtained by the single factor test increased by 10.11%. When the ultrasonic treatment time was 25 min, the corresponding DPPH value of dried L. barbarum producta obtained by the single factor test increased by 14.33%; By comparing the microstructure diagrams under different processing conditions, it was found that ultrasonic waves can not only increase the number of micropores in the surface of materials, but also reduce the damage to L. barbarum epidermal cells. Conclusion: The application of ultrasonic technology to the far-infrared vacuum drying of L. barbarum strengthens the heat and mass transfer process inside and improves the quality of L. barbarum dried fruit, which can provide technical guidance for the development of L. barbarum drying technology.