热风与微波及其联合干燥对菠菜干制效果的影响

分别采用不同热风温度、不同微波功率和热风与微波联合的方法对菠菜进行干燥，研究热风干燥与微波干燥及其联合干燥对菠菜复水性、VC保留及色值的影响。结果表明：最佳干燥工艺为前期采用50℃热风干燥，转换点含水率为60%，后期采用功率540W进行微波干燥；在此条件下，联合干燥比热风干燥缩短了干燥时间约40%～50%，VC保留率提高了39.1%～44.3%，菌落总数降低到3.59～4.51(lg(CFU/g))，产品的水分含量为8%(湿基)。说明热风微波联合干燥可以很好地保持菠菜的品质，同时使菌落总数降至安全范围。

Separate and Joint Effects of Hot Air Drying and Microwave Drying on Properties of Spinach

In order to evaluate the separate and joint effects of hot air drying and microwave drying on the rehydration ratio, VC retention and color parameters of spinach, fresh spinach was dried under different hot air temperatures, different microwave powers or their combinations. The results showed that the optimal drying process involved hot air drying at 50 ℃ for a water content of 60% at the transition point and subsequent microwave drying at 540 W. Under these conditions, the drying time was shortened by 40%－50% than that required for hot air drying. Moreover, VC retention was increased by 39.1%－44.3% and total viable count was decreased to 3.59－4.51 (lg(CFU/g)). The resulting product had a water content of 8% (calculated on wet basis). These findings suggest that combined hot air drying and microwave drying can maintain the quality of spinach well and reduce the total viable count to meet the safe range.