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.