青花椒热泵干燥特性及工艺参数优化

为了探究青花椒热泵干燥特性并优化干燥工艺参数以提高干制花椒品质，本文以温度、风速和铺放厚度为试验因子，以有效水分扩散系数、光合色素单位质量含量和色差为评价指标，对青花椒热泵干燥过程进行单因素试验和正交试验，并采用6种常用干燥数学模型分别对正交试验数据进行非线性拟合。结果表明，Page模型对试验数据的拟合度最好，是描述青花椒热泵干燥的最佳模型；在恒温干燥条件下，温度对有效水分扩散系数和色差的影响极显著（P<0.01），温度越高，有效水分扩散系数和色差变化越大；风速对色差的影响显著（P<0.05），风速越大，色差变化越大；铺放厚度对色差的影响极显著（P<0.01），铺放厚度越大，色差变化越小；而光合色素单位质量含量在不同温度条件下均具有先略下降再上升后又迅速下降至稳定的趋势，温度越高，光合色素单位质量含量变化越快，不利于干制青花椒品质的提高。综合考虑温度、风速、铺放厚度对青花椒色差、光合色素单位质量含量和有效水分扩散系数的影响，确定最优干燥工艺参数为温度40 ℃、风速0.3 m/s、铺放厚度11.9 mm，在此条件下，干制青花椒色泽品质最佳，色差为20.01，光合色素单位质量含量为2.9601×10?4 mg/g。研究结果可为青花椒热泵干燥工艺应用提供参考。

Drying Characteristics and Process Optimization by Heat Pump Drying of Green Sichuan Pepper

In order to investigate the drying characteristics of green Sichuan pepper by heat pump and optimize the drying process parameters to improve the quality of dried green Sichuan pepper, the single-factor experiments and orthogonal tests on the drying process of green Sichuan pepper were conducted in this study. Temperature, air speed and laying thickness were defined as test factors, and effective moisture diffusion coefficient, photosynthetic pigment unit mass content and color difference were determined as evaluation indexes. Six commonly used drying mathematical models were used to fit the orthogonal test data nonlinearly, respectively. The results showed that the Page model had the best fit to the test data and it was the best model to describe the drying of green Sichuan pepper by heat pump. Under the constant temperature drying condition, the effect of temperature on the effective moisture diffusion coefficient and color difference was highly significant (P<0.01). The higher the temperature, the greater the change of effective moisture diffusion coefficient and color difference. The effect of air speed on color difference was significant (P<0.05). The higher the air speed, the greater the change of color difference. The effect of laying thickness on color difference was highly significant (P<0.01). The higher the laying thickness, the greater the color difference. However, under different temperatures the unit mass content of photosynthetic pigment slightly decreased, and then increased, and then rapidly decreased until it reached stability. The higher the temperature, the faster the change of the unit mass content of photosynthetic pigment, which was not beneficial to the quality improvement of dried green Sichuan pepper. By comprehensively the effects of temperature, air speed and laying thickness on the color difference, unit mass content of photosynthetic pigment and effective moisture diffusion coefficient, the optimal parameters of drying process were determined as temperature of 40 ℃, air speed of 0.3 m/s and laying thickness of 11.9 mm. Under these conditions, the best color quality of dried green Sichuan pepper was achieved, with a color difference of 20.01 and a photosynthetic pigment unit mass content of 2.9601×10?4 mg/g. The results of the study could provide reference for the application of heat pump drying process of green Sichuan pepper.