【摘要】 为揭示果蔬低压过热蒸汽干燥过程水分传输机理，利用低场核磁共振技术对80℃，0.009 5 MPa干燥1,2,3 h的青萝卜块水分分布特点进行研究。结果显示，青萝卜块中90%以上的水分为自由水，在干燥过程中T₂₃值由690逐渐降至110,T₂₂值在干燥前2 h由48逐渐升至61，随后降至33,T₂₁值在干燥过程中都处于5以下且变化较小。整个干燥过程青萝卜块边缘位置信号强度快速下降并形成明显的边界，说明在干燥过程中自由水首先蒸发，并有一小部分自由水转变为中度结合水，当自由水降至一定含量时，中度结合水开始蒸发，不易流动水的蒸发主要在干燥后期，且自由水在原位直接以气态形式蒸发。研究结果明确了果蔬低压过热蒸汽干燥过程水分传递特点，为精准建立干燥过程数学模型提供理论基础。更多还原

【Abstract】 In order to reveal the mechanism of water transport during low-pressure superheated steam drying of fruits and vegetables,low field nuclear magnetic resonance technology （LF-NMR） was used to study the water distribution characteristics of green turnip blocks dried at 80℃，0.009 5 MPa for 1 h,2 h and 3 h.The results show that more than 90%of the water in the green turnip blocks is free water.During the drying process,the T₂₃ value gradually decreases from 690 to 110,the T₂₂ value increases from 48 to 61 in the first 2 h of drying,and then gradually decreases to 33,and the T₂₁ value is always below 5 during the drying process with a small range of change.During the whole drying process,the signal intensity at the edge position of the green turnip blocks decreases rapidly and forms a clear border.This indicates that the free water evaporates first,and a small part of free water will change into moderately bound water.The moderately bound water begins to evaporate when the free water decreases to a certain content.The evaporation of non-flowing water is mainly in the later stage of drying,and free water is evaporated in situ in gaseous form directly.The research results clarify the characteristics of water transfer during the low-pressure superheated steam drying process of fruits and vegetables,and provide a theoretical basis for the accurate establishment of the mathematical model of the drying process.更多还原