Effects of Short- and Medium-wave Infrared Radiation Drying on Drying Characteristics, Nutritional Quality and Antioxidant Activity of Mulberry

In order to explore the effects of short-and medium-wave infrared radiation drying on the drying characteristics, energy consumption, nutritional quality and antioxidant activity of mulberry, fresh mulberry was dried by short- and medium-wave infrared radiation drying at different drying temperatures (50, 60, 70 ℃), and compared with hot air drying under the same drying temperature (50, 60, 70 ℃), the drying characteristics, energy consumption, contents of phenolic monomers, total phenols, total flavonoids, vitamin C, total anthocyanin and antioxidant activity of mulberry under different drying conditions were investigated, and the short- and medium-wave infrared drying mathematical model of mulberry fruit was established. The results showed that the short- and medium-wave infrared radiation drying could significantly improve the drying efficiency of mulberry (the drying efficiency increased by 55.7% at 50 ℃, 46.1% at 60 ℃, and 33.3% at 70 ℃), and the Weibull distribution model could well simulate the drying process of short- and medium-wave infrared radiation drying at different drying temperatures. In addition, the energy consumption of mulberry dried by medium and short wave infrared was lower. Twelve phenolic substances were detected in dried mulberry fruit, among which chlorogenic acid, rutin and catechin were the main phenolic substances. Compared with the traditional hot air drying, the short-and medium-wave infrared radiation drying had higher drying efficiency, higher contents of total phenols, total flavonoids, vitamin C and total anthocyanins, the total phenol content was 463.1~568.8 mg/100 g. The total flavonoids content was 312.6~402.6 mg/100 g. The contents of vitamin C was 30.1~37.8 mg/100 g. The total anthocyanin content was 153.6~195.6 mg/100 g. In addition, compared with hot air drying, the antioxidant activity of mulberry fruit was significantly enhanced after short- and medium-wave infrared radiation drying (DPPH free radical scavenging ability was improved by 32.8% to 42.6% compared with hot air drying). Compared with hot air drying, iron ion reduction ability was improved by 21.1%~34.1%), short- and medium-wave infrared radiation drying of mulberry fruit had higher drying efficiency, lower energy consumption and better quality of dried products. Therefore, short- and medium-wave infrared radiation drying was an excellent drying way of mulberry fruit, which could provide theoretical reference for the dried processing of mulberry fruit.