Effect of Direct-Contact Ultrasonic and Far Infrared Combined Drying on the Drying Characteristics and Quality of Ginger

In this study, the effects of ultrasonic power, drying temperature, and slice thickness on the drying rate, chromatism, water migration law, gingerol content, flavor, and antioxidant activity of ginger were investigated by using a direct-contact ultrasound and far infrared combined drying technology. The results showed that compared with single far infrared drying, direct-contact ultrasound and far infrared combined drying accelerated the free water migration rate of ginger (7.1 similar to 38.1%), shortened the drying time (from 280 min to 160 min), reduced the loss of volatile components in ginger, and significantly increased the antioxidant activity of ginger (p < 0.05). Furthermore, after ultrasound intervention, the gingerol content decreased in slices of 4 mm thickness (0.1226 +/- 0.0189 mg/g to 0.1177 +/- 0.0837 mg/g) but increased in slices of 6 mm thickness (0.1104 +/- 0.0162 mg/g to 0.1268 +/- 0.0112 mg/g). This drying technology has a certain reference significance for the drying process of ginger slices.