Experiments on microwave drying of carrot slices using pulsed electric field pre-treatment

In order to study the effects of pulsed electric field (PEF) pre-treatment on microwave drying characteristics of carrot slices, according the experiment indexes of average drying rate and rehydration ratio of carrot slices, four factors (pulse frequency, electric field strength, microwave power intensity and thickness), quadratic regression orthogonal experiments on microwave drying of carrot slices with PEF pre-treatment were conducted. The curves of dehydration rate of microwave drying carrot slices were obtained. The equations of drying kinetics and indexes were gotten by regression analyzing with SPSS, and the indexes were synthetically optimized as well. The results showed that the Page's model was better for the microwave drying kinetics of PEF pre-treated carrot slices; the average drying rate was markedly influenced by pulse frequency and electric field strength; the rehydration ratio was markedly affected by pulse frequency, but it was not done by electric field strength. The optimal combinations of parameters were pulse frequency 30 Hz, electric field strength 2.0 kV/cm, microwave power intensity 1.0 W/g and thickness 4.0 mm. Under the optimal condition, the average drying rate and rehydration ratio of carrot slices were improved.