Evaluation of the effect of ultrasonic pretreatment on vacuum far-infrared drying characteristics and quality of Angelica sinensis based on entropy weight-coefficient of variation method.

This study investigated the effects of ultrasonic pretreatment time, ultrasonic power, and ultrasonic frequency on the drying characteristics and physicochemical quality of Angelica sinensis, and the physicochemical quality content was selected as the evaluation index, the entropy weight-coefficient of variation method was used to calculate the coupling weight and comprehensive score, and the weighted Technique for Order Preference by Similarity to Ideal Solution method was used to verify the evaluation model. The results showed that the drying rate of materials after ultrasonic treatment was increased by 22.48% to 93.26%, and the effective moisture diffusivity was in the range between 4.6831 × 10-9 and 7.0722 × 10-9  m2 /s, and the drying activation energy was 31.90 kJ/mol. The energy consumption decreased by 5.75% to 25.88%. Compared with the samples without the ultrasonic pretreatment, the chlorogenic acid, ferulic acid, senkyunolide H, senkyunolide I, 3-butenylphthalide, ligustilide, polysaccharides, total phenolic content, total flavonoid content, and antioxidant capacity of A. sinensis were increased after ultrasonic treatment, and the color, rehydration ratio, shrinkage ratio, and microstructure of dried products were improved significantly (p < 0.05). However, the quality of the dried products decreased after ultrasonic treatment for 40 min with an ultrasonic frequency of 60 kHz, and the internal tissue structure was destroyed. In summary, ultrasonic pretreatment at low frequency and high power can significantly increase the drying rate and improve the physicochemical quality of dried products.

Improving Drying Characteristics and Physicochemical Quality of Angelica sinensis by Novel Tray Rotation Microwave Vacuum Drying.

In order to improve the shortcomings of uneven heating of traditional microwave drying and to maximally maintain food quality after harvest, a rotary microwave vacuum drying equipment was fabricated and used for drying experiments on Angelica sinensis to explore the effects of drying temperature, slice thickness, and vacuum degree on drying characteristics, physicochemical quality, and microstructure of dried Angelica sinensis products. The results showed that microwave vacuum drying can significantly shorten the drying time and improved the drying efficiency. Six different mathematical models were investigated and the Midilli model was the best-fitted model for all samples (R2 = 0.99903, Pearson's r = 0.99952), and drying methods had various effects on different indexes and were confirmed by Pearson's correlation analysis and principal component analysis. The optimal process parameters for microwave vacuum drying of Angelica sinensis were determined by entropy weight-coefficient of variation method as 45 °C, 4 mm, -0.70 kPa. Under this condition, well preserved of ferulic acid, senkyunolide I, senkyunolide H, ligustilide, total phenols and antioxidant activity, bright color (L* = 77.97 ± 1.89, ΔE = 6.77 ± 2.01), complete internal organizational structure and more regular cell arrangement were obtained in the samples. This study will provide a theoretical reference for the excavation of the potential value and the development of industrial processing of Angelica sinensis.