Moisture distribution change and quality characteristics of ultrasound enhanced heat pump drying on carrot

The study aims at investigating the impact of ultrasound enhancement on the water change and quality characteristics of dried carrots by heat pump drying (HPD). The results showed that ultrasound had obvious strengthening effect on the drying and dehydration process of HPD, but there was an attenuation effect of ultrasound in the propagation process of materials, and the magnetic resonance imaging results could visually demonstrate the change and migration of moisture inside carrot slices. Higher drying temperature and ultrasonic power could cause more micropores and higher content of polyphenols, flavonoids and niacin of carrot slices. Conversely, the elevated drying temperature reduced rehydration ratio. beta-carotene content showed a trend of increasing first and then decreasing due to excessive temperature and ultrasonic power. Based on AHP-CRTITC method, the highest comprehensive score was attained at drying temperature of 60 degrees C and ultrasonic power of 80 W. Therefore, the reinforcement effect of ultrasound on HPD process could significantly enhance dehydration rate and improve product quality.