为减少脱水蔬菜冷冻干燥过程的能耗,以胡萝卜片为试材,采用真空微波和冷冻干燥组合的工艺,即先微波真空后冻干(组合Ⅰ)和先冻干后微波真空干燥(组合Ⅱ).组合Ⅰ的优化参数为:真空微波阶段微波功率密度1.6 w/g,脱去40个百分点的湿基水,冻干阶段升华干燥4 h,解析干燥3 h；组合Ⅱ的优化参数为:冻干阶段升华干燥7 h；真空微波干燥功率密度选1.0 w/g以下,采用温度控制模式.所干燥胡萝卜片的β-胡萝卜素保留率和复水率等与纯冻干产品接近,体积保留率比纯冻干稍小,但仍能保持平直的外形；2种组合干燥工艺比纯冻干分别节能47.0％和54.2％,且干燥时间可缩短一半.%In order to reduce the energy consumption during freeze drying (FD) of vegetables, vacuum microwave drying (VMWD) was introduced and applied before or after FD, which is referd to combination I and combination II respectively. For combination I , the optimized microwave power density, moisture content removed during VMWD, sublimation drying time and desorption drying time during FD were 1.6 W/g, 40%, 4 h, and 3 h, respectively. For combination II, the optimized sublimation drying time and microwave power density of VMWD were 7 h, and 1.0 W/g respectively; and temperature control mode was adopted for VMWD. Moreover, the color, the retention of β-carotene and rehydrated ratio of carrot slices by combined drying were very close to those of FD, but the volume retention ratio was slightly less than that of FD while still maintaining an acceptable appearance. Compared with FD, energy consumption of the two combined drying methods was saved by 47.0% and 54. 2% respectively, and the drying time was saved by 50%.
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