Microwave-vacuum Drying Kinetics Model and Quality Analysis of Chinese Chestnut Slice
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Abstract:
In order to obtain chestnut products with a fast drying rate and high quality, fresh Chinese chestnut was used as the raw material for microwave-vacuum drying. The drying characteristics of chestnut slices under different vacuum degrees and microwave powers were investigated. Based on the experimental data, the kinetic model for the relationship between the moisture ratio and drying time of the microwave-vacuum dried chestnut slices was established and then tested by fitting. At the same time, the quality of chestnut slices prepared under different drying conditions was evaluated. The results showed that both the microwave power and vacuum degree had a significant influence on the drying time: the higher the microwave power, the higher vacuum degree, the faster the drying. In the test range, the effective diffusion coefficient of moisture increased with the rise of drying microwave power and with the increase of vacuum degree, with the effect of microwave power on the effective diffusion coefficient of moisture being more significant than that of vacuum degree. Using the Fick’s second law of diffusion, the range of moisture effective diffusivity (Deff) was 3.5462×10-9~2.128×10-8 m2/s. The Page model was found to be the best to simulate microwave-vacuum drying of chestnut slices among the four mathematical models. By fitting the mathematical drying kinetics model of chestnut slices, it was found that the Page model exhibited the best fit to the drying process of chestnut slices, with the predicted value of the model in good agreement with the experimental value, therefore, can be used to describe and predict the microwave-vacuum drying process of chestnut slices. Chinese chestnut slices dried under a vacuum degree of -20 kPa and microwave power of 3 kW had the greatest brightness (L* value: 71.77) and the best texture, and differed significantly from those obtained under other drying conditions (p<0.05). This study provides a technical basis for the application of microwave-vacuum drying technology in chestnut drying.
