Abstract: In order to study the effects of infrared radiation hot air coupled drying (IRHA) on Acetes chinensis drying characteristics, low field nuclear magnetic resonance spectroscopy (NMR) and hydrogen proton imaging (MRI) were used to analyze the combination form of dry matters and water, as well the drying characteristics under different drying temperature, radiation distances and material loads. The results showed that drying temperature had a major impact on the drying rate of acetes and the drying process entered the slowdown drying stage directly. Mathematical models were selected to fit the drying process, and the Two-term model (R²>0.999 8) was found to have the highest degree of fit to the drying process, which could be used to describe and predict the IRHA drying process. Moisture diffusivity is an important indicator of the internal moisture transfer during the drying process. The Fick’s second law of diffusion was employed to calculate the value of moisture effective diffusivity coefficient (D_eff), which ranged from 4.47×10^-10 m²·s^-1 to 1.295×10^-9 m²·s^-1 with the temperature of 50~80℃. The activation energy determined with Arrhenius equation was 34.24 kJ·mol^-1 for the drying of acetes by IRHA drying, which was in the reasonable range. The dry matter of acetes was combined more and more tightly with water during the drying process, and free and non-flowable water gradually disappeared. At the end of drying, only the combined water existed, and the amount of combined water increased, which might result from the conversion of the non-flowable water. This explained microscopically the reason for the decrease in drying rate in the late drying stage from microcosmic level. This research provided theoretical and technical foundation for IRHA drying of acetes.

Key words: Acetes chinensis, infrared radiation hot air coupled drying, drying kinetics, activation energy, low field nuclear magnetic resonance

摘要： 为研究红外热风耦合干燥(IRHA)对中国毛虾干燥特性的影响,采用低场核磁共振波谱(NMR)及氢质子成像技术(MRI)分析毛虾IRHA干燥过程中干物质与水结合状态,分析不同干燥温度、不同辐射距离和不同物料载量下IRHA对中国毛虾的干燥特性。结果表明,干燥温度对毛虾的干燥速率影响最大,干燥过程直接表现为降速阶段。毛虾干燥动力学数学模型拟合表明,Two-term模型拟合度最高(R²>0.999 8),可以用来描述和预测毛虾IRHA干燥过程。通过菲克第二定律求得干燥过程的有效水分扩散系数(D_eff)范围为4.47×10^-10~1.295×10^-9 m²· s^-1。根据Arrhenius公式计算出毛虾IRHA干燥的活化能(E_a)为34.24 kJ· mol^-1。干燥过程中毛虾干物质与水结合越来越紧密,自由水和不易流动水逐渐消失,最终只存结合水,且结合水的量有所上升,有可能来自不易流动水的转化,这从微观上解释了干燥后期干燥速率下降的原因。本研究结果为IRHA在中国毛虾干燥方面的实际应用提供了一定的理论依据。

关键词: 毛虾, 红外热风耦合干燥, 干燥动力学, 活化能, 低场核磁共振