板栗片微波真空干燥的动力学模型及品质分析

Microwave-vacuum Drying Kinetics Model and Quality Analysis of Chinese Chestnut Slice

为获得干燥速率快、品质高的板栗制品,以新鲜板栗为原料对其进行微波真空干燥处理。研究了板栗片在不同真空度、微波功率条件下的微波真空干燥特性。根据试验数据建立板栗微波真空干燥的水分比与干燥时间关系的动力学模型,对模型进行拟合检验,同时对不同干燥条件的板栗品质进行评价。结果表明:微波强度和真空度均对干燥时间有显著影响,功率越大,真空度越高,干燥速率越快。在试验范围内水分有效扩散系数随着真空度升高而升高,随着微波功率的升高而升高,而且功率对板栗水分有效扩散系数的影响比真空度更显著。利用Fick第二定律求出其范围为3.5462×10^-9~2.128×10^-8m^2/s。通过对板栗干燥动力学数学模型拟合发现,Page模型对板栗片干燥过程的拟合性最好,模型的预测值与实验值吻合性好,可以用来描述和预测板栗的微波真空干燥过程。在真空度-20 kPa、微波功率3 kW干燥条件下,板栗片的亮度L*值最大为71.77且板栗片的质地最优,与其他干燥条件下有显著差异(p<0.05),。该研究为微波真空干燥技术应用于板栗的干燥提供了技术依据。

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 m^2/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.