Abstract:[Objective]This study aimed to improve the quality and drying efficiency of hot air-dried mulberries.[Method]Mulberries were pretreated with different pressure levels (0~300 MPa). The effects on drying characteristics, water distribution, cellular structure, and active components were systematically investigated through low-field nuclear magnetic resonance (LF-NMR), microscopic structural observation, quantitative analysis of cell wall components, active compound determination, and principal component analysis of electronic nose data.[Result]The key pressure threshold was identified at 150 MPa. Under this condition, the free water ratio reached its peak (T23 peak area accounted for 47.3%). Selective rupture of the cell wall-membrane system formed interconnected cavities, significantly increasing porosity. The mass fraction of cellulose gradually decreases as pressure increases, stabilizing at 250 MPa (10.28 mg/g). The protopectin kept degrading (down to 10.25 mg/g at 300 MPa), and that of soluble pectin gradually increased to 11.81 mg/g, indicating that pectin degradation induced by high pressure dominated structure changes in the cell wall. Ultra-high pressure pretreament resulted in a reduction of 38.5% in drying time and significantly improved the retention of active compounds (mass fraction of flavonoid: 1.01 mg/g; mass fraction of total phenols: 0.32 mg/g). Electronic nose analysis revealed the greatest flavor change occurred at 300 MPa.[Conclusion]Considering both quality and drying efficiency, 150 MPa was selected as the optimal pretreatment condition. It exerts the synergistic effects of cellular structural reorganization, water state transformation, and degradation of cell wall components in improving the drying process. This study provides a theoretical basis for the high-value processing of mulberries.
