RESUMO
Objective: To shorten the drying time of Lycium barbarum, increase its shelf life, improve the quality of dried L. barbarum products, and provide technical support for the development of wolfberry drying industry. Methods: Using L. barbarum as experiment material, after being permeated, ultrasonic treating, blanching, ultrasonic treating + permeation and ultrasonic treating + blanchting, far infrared drying test was carried out. The effects of different pretreatment methods on the far-infrared drying characteristics of L. barbarum were studied. Weibull distribution function was used to fit the drying process. The quality and microstructure of dried L. barbarum products were analyzed. Results: After being pretreated, the drying time of L. barbarum was significantly reduced, the drying rate was increased; Compared with L. barbarum without pretreatment before pre-dried, drying time after blanching pretreatment shortened 27.5%, the moisture ratio of the material decreased fastest, and drying rate was the highest. Weibull distribution function can simulate the far infrared drying process of L. barbarum under different pretreatment conditions. The range of r2 and χ2 was 0.991 73-0.999 15 and 8.13 41 × 10-5-8.846 79 × 10-4. The drying characteristics described by scale parameter (α) and shape parameter (β) were consistent with those in the drying characteristic curve. The dried product pretreated with ultrasound + permeation had the smallest color difference (6.756 4) compared with the fresh sample. The polysaccharide content inside the material (991.27 mg/g•DW) was the highest; The microstructure of the dry product obtained by the ultrasound + penetration group had the most voids, and the drying treatment had the least damage to its surface. Conclusion: Ultrasonic and osmotic pretreatment of L. barbarum before drying can not only shorten the drying time, but also improve the quality of its dried products.
RESUMO
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.