title: Power ultrasound as a pretreatment to convective drying of mulberry (Morus alba L.) leaves: Impact on drying kinetics and selected quality properties.
abstract: The effect of ultrasound pretreatment prior to convective drying on drying kinetics and selected quality properties of mulberry leaves was investigated in this study. Ultrasound pretreatment was carried out at 25.2-117.6 W/L for 5-15 min in a continuous mode. After sonication, mulberry leaves were dried in a hot-air convective dryer at 60 °C. The results revealed that ultrasound pretreatment not only affected the weight of mulberry leaves, it also enhanced the convective drying kinetics and reduced total energy consumption. The drying kinetics was modeled using a diffusion model considering external resistance and effective diffusion coefficient De and mass transfer coefficient hm were identified. Both De and hm during convective drying increased with the increase of acoustic energy density (AED) and ultrasound duration. However, De and hm increased slowly at high AED levels. Furthermore, ultrasound pretreatment had a more profound influence on internal mass transfer resistance than on external mass transfer resistance during drying according to Sherwood numbers. Regarding the quality properties, the color, antioxidant activity and contents of several bioactive compounds of dried mulberry leaves pretreated by ultrasound at 63.0 W/L for 10 min were similar to that of mulberry leaves without any pretreatments. Overall, ultrasound pretreatment is effective to shorten the subsequent drying time of mulberry leaves without damaging the quality of final product.
authors.affiliation: College of Food Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Tao
authors.affiliation: College of Food Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Wang
authors.affiliation: College of Food Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Yilin
authors.initials: Y
authors.lastname: Wang
authors.affiliation: UCD School of Biosystems and Food Engineering, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Shekhar U
authors.initials: SU
authors.lastname: Kadam
authors.affiliation: College of Food Science and Technology, Nanjing Agricultural University, Nanjing 210095, China. Electronic address: hanyongbin@njau.edu.cn.
authors.forename: Yongbin
authors.initials: Y
authors.lastname: Han
authors.affiliation: College of Food Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Jiandong
authors.initials: J
authors.lastname: Wang
authors.affiliation: Institute of Agro-product Processing, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China.
authors.forename: Jianzhong
authors.initials: J
authors.lastname: Zhou
mesh_terms: D007700:Kinetics; D031625:Morus / Q000737:chemistry*; D018515:Plant Leaves / Q000737:chemistry*; D014465:Ultrasonics
keywords: Convective drying; Drying kinetics; Mulberry leaves; Quality property; Ultrasound pretreatment