Effect of Carbonic Maceration Treatment on Vacuum-microwave Drying Characteristics and Microstructure of Ginger
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Abstract:
In order to study the effects of carbon dioxide impregnation (CDI) on the microwave-vacuum drying characteristics and microstructure of ginger, different temperatures (35, 40, 45 ℃), pressures (1, 2, 3 MPa) and treatment times (3, 5, 7 h) were selected for CDI to pretreat ginger. The changes in moisture ratio, drying rate, effective diffusion coefficient of ginger during drying were measured, and the mathematical model for thin layer drying was fitted. In addition, the microstructures of ginger under different CDI conditions were also studied. The results showed that after CDI, the rate of drying ginger significantly increased, especially in the late drying stage. When the ginger was pretreated at 2 MPa and 45 ℃ for 7 h, the moisture diffusion was the fastest, and the drying time was shortened by 47% compared to that for the sample dried directly. Among the five thin layer drying models, the Modified Page model exhibited the best fit to the changes in ginger’s moisture content during drying, based on the coefficient of determination (R2), chi-square (χ2) and root mean square error (RMSE). Scanning electron microscopy revealed that CDI increased the cell area and porosity of ginger tissues, and enhanced the mass and heat transfer of the material. Therefore, CDI had a positive effect on improving the internal structure and drying efficiency of ginger. The results obtained in this study provide the theoretical basis for the development of new drying technologies for ginger.
