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.