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By using ultrasonic synergy vacuum far‐infrared drying (US‐VFID), the effects of different conditions on the drying kinetics, functional properties, and microstructure of Codonopsis pilosula slices were studied. The sparrow search algorithm (SSA) was used to optimize the back‐propagation (BP) neural network to predict the moisture ratio during drying. With the increase of ultrasonic frequency, power and radiation temperature, the drying time of C. pilosula was shortened. The drying time of US‐VFID was 25% shorter than VFID, when radiation temperature was 50°C, ultrasonic power was 48 W, and frequency was 28 kHz. The SSA‐BP neural network, the average absolute error prediction was 0.0067. Compared with hot air drying (HAD), the total phenolic content and antioxidant activity of C. pilosula by US‐VFID were increased by 29.47% and 8.67%, respectively, and a reduction in color contrast of 16.19%. The dilation and generation of microcapillary of C. pilosula were more obvious. The study revealed US‐VFID could be used for the selection and process control of agro‐processing methods for C. pilosula products. [ABSTRACT FROM AUTHOR]

Ultrasonic (US) maltreatment was performed before the vacuum far-infrared drying (VFID) of Codonopsis pilosula (CP) slices to investigate the effects of different US parameters on the drying characteristics and nutrients of CP slices. The grey correlation method with relative correlation degree (ri) as the evaluation measure was used to construct a model for the evaluation of the pretreatment quality of CP and to determine the optimal pretreatment conditions. The results showed that with the increase in US frequency and power, the drying rate increased. Under the conditions of US power of 180 W, frequency of 60 kHz and a pre-treatment time of 30 min, the drying time reduced by 28.6%. The contents of polysaccharide and syringin in dried CP slices pretreated by US increased by 14.7% and 62.0%, respectively, compared to the non-pre-treated samples, while the total flavonoid content decreased by 10.0%. In terms of colour, pretreatment had a certain protective effect on the red colour of dried products. The highest relative correlation (0.574) and the best overall quality of performance were observed at 180 W, 60 kHz and 30 min. Overall, US technology is suitable for the pretreatment processing of CP, which is of great significance to the drying of CP. [ABSTRACT FROM AUTHOR]

In this paper, the effects of ultrasonic pretreatment on the drying kinetics, bioactive components (polysaccharides, total phenols, total flavonoids and antioxidant), qualitative characteristics (color index, lobetyolin and syringin) and microstructure of Codonopsis pilosula during radio frequency vacuum drying (RFVD) were studied. The average drying rate curve showed that the whole drying process could be divided into three stages: accelerating period, constant drying rate period and falling drying rate period. Deff values ranged from 6.61425 to 9.46745 × 10−8. Analysis of the drying rate constants revealed that different conditions of pretreatment were effective in increasing the drying rate. Ultrasonic pretreatment has a positive effect on the retention of polysaccharide content; low frequency favors retention of total phenols, flavonoids and syringin; and with the increase in ultrasonic time and ultrasonic power, the antioxidant capacity was higher than that without ultrasonic treatment. Ultrasonic pretreatment significantly improved color and microstructure. In summary, the pretreatment condition of ultrasonic frequency 20 kHz and power 60 W for 30 min is suitable, which provides a certain reference for the application of ultrasonic pretreatment technology in RFVD of Codonopsis pilosula slices. [ABSTRACT FROM AUTHOR]