热泵微波联合干燥对刺参干燥特性和品质特性的影响

Influences of Combined Heat Pump and Microwave Drying on Drying Characteristics and Product Quality of Sea Cucumbers

为了改善热泵干燥时间过长、微波干燥成品品质差的问题,研究了热泵微波联合干燥对刺参干燥特性和品质特性的影响,提出了具有不同干燥温度和不同转换点含水率的多种热泵微波联合干燥方式,并通过实验方式研究了刺参的含水率、干燥速率、收缩率、复水率、外观、组织形态、气味等参数的变化规律.结果表明,热泵微波联合干燥呈现明显的分段变化特征,微波干燥阶段最大干燥速率远高于热泵干燥,分段薄层干燥模型可以较好地模拟刺参的干燥特性.在干制品性能方面,相同干燥温度下,纯热泵干燥成品的复水率小于联合干燥,但收缩率大于联合干燥.在热泵微波联合干燥中,干制品的复水率随干燥温度的升高而逐渐降低,但收缩率逐渐增加.热泵微波联合干燥中转入微波干燥的时间点需综合干燥时间和成品性能来综合确定,对应40℃干燥温度,转换点含水率为197%时,干燥成品品质最好,干燥时间也较短,是一种较好的刺参联合干燥方式.

To overcome the shortcomings of long hours in heat pump drying and low qualities in microwave drying, the combined heat pump and microwave drying is introduced in sea cucumber drying. Several combined drying processes are put forward with different drying temperatures and transition moisture contents. A series of experiments are made to study the drying characteristics of drying process and dried products for sea cucumbers under combined drying, including the variations of moisture contents, drying rates, shrinkage ratios, rehydration ratios, appearances, forms of organization, odours, etc. Results show that the combined drying processes show apparent two-period features in the combined drying, with higher drying rates in the microwave drying period than that in the heat pump drying period, which is perfectly described by a two-stage thin layer drying model. For the drying performances of dried products, higher rehydration ratio and lower shrinkage ratios in the combined drying are found than those in the heat pump drying. With the increasing drying temperature, the rehydration ratio decreases and shrinkage ratio increases in the combined drying. During the combined drying of sea cucumbers, the transition moisture content should be integrally determined according to both the drying time and product performances. For the 40℃ drying temperature, the combined drying with 197% of transition moisture content gets better product performances and relatively short drying time, which is a preferable drying process for sea cucumbers.