微波干燥过程中的土豆组织温度变化及水分迁移特性

为探索淀粉类果蔬多孔介质在微波干燥过程中的热质传递特性,以土豆为研究对象,测量其不同功率下微波干燥过程中土豆组织的温度和质量以及水分状态变化。结果表明,微波干燥过程中土豆组织的温度可以分为快速升温、恒温及降温段3个阶段,土豆质量减少主要发生在恒温段,且该阶段物料的失重率占总失重率的90%以上。微波干燥过程中自由水短暂升高至93.21%后逐渐降低至15.61%,而不易流动水和结合水均先降低后升高。淀粉对于微波干燥中的水分迁移有重要影响,淀粉失去薄膜水后固化,使得土豆片的骨架硬度增加,从而增大水分迁移阻力。

Temperature Change and Moisture Transfer Characteristics of Potato Tissue during Microwave Drying

In order to explore the heat and mass transfer characteristics of porous medium of starchy fruits and vegetables during the microwave drying process, the temperature, mass and water status changes of potato tissue were measured during microwave drying at different powers. The results showed that, the temperature of potato tissue during microwave drying could be divided into three stages: rapid heating, constant temperature and cooling. The reduction of potato mass mainly occurred in the constant temperature section, and the weight loss rate in this stage accounted for more than 90% of the total weight loss. During the microwave drying process, the free water temporarily increased to 93.21% and then gradually decreased to 15.61%, while the non-flowable water and bound water firstly decreased and then increased. Starch had an important effect on the moisture migration during microwave drying, starch solidified when losing bound water, which increased the skeleton hardness of potato chips and thereby enhanced the moisture migration resistance.