Microwave drying characteristics of potato and the effect of different microwave powers on the dried quality of potato

Abstract

Little detailed information is available on the microwave drying characteristics of potato and the use of different microwave powers to dry food products. Experiments were conducted to study the microwave drying characteristics and the dried quality of potato. The study focuses on describing the microwave drying characteristics of potato and discussing the effect of sample thickness, drying power and mass. The results show that if the power level increases, the mass load decreases and the thickness of the sample decreases, the dehydration rate increases and the drying energy consumption decreases. There are two falling rate periods during microwave drying of potato: the first falling rate period is for a moisture content of more then 1.1 (dry basis, DB); the second falling rate period is for a moisture content of less than 1.1 (DB). The same water loss will consume more energy when the moisture content is less than 1.1 (DB). A two-stage drying process was employed during microwave drying of potato. The microwave power of the first drying stage differed form that of the second drying stage. The moisture content of the breakpoint for the conversion of the first drying stage into the second drying stage is a moisture content of 1.1 (DB). A quadratic orthogonal regression experiment was conducted, and the effects of slice thickness, the first drying load power and the second drying load power on sensory quality, the rehydration ratio and the energy consumption rate were established. The slice thickness, the first drying load power and the second drying load power linearly affected the three indices. The effect of the product of the second drying load power and the potato slice thickness on the rehydration ratio and the energy consumption rate is significant. The optimum drying parameter combination for the three indices was obtained. The rehydration ratio of the dried products decreased with an increase of the second drying load power and the slice thickness. The concave curves of the sensory quality versus the three factors were shown.