THE EFFECT OF MICROWAVE OUTPUT POWER ON DRYING KINETICS OF YOGHURT AND MATHEMATICAL MODELING OF DRYING CURVES

The objectives of this study were to investigate the effects of microwave output powers on drying kinetics of yoghurt, selecting the best fitted thin-layer model to characterize the drying behavior of yoghurt and determination of the activation energy and effective diffusivity. In order to achieve these objectives, low-fat yoghurt was dried by using domestic microwave oven at different microwave output powers (100, 180 and 300 W). The average drying rates were determined as 1.49, 4.43 and 7.90 g H2O m(-2) s(-1) for microwave output powers of 100, 180 and 300 W, respectively. The effective moisture diffusivities were determined as 3.30 x 10(-9), 6.62 x 10(-9) and 1.15 x 10(-8) m(2) s(-1) for 100, 180 and 300 W, respectively. The Ea of yoghurt was found as 3.62 W g(-1). Midilli and others model was selected as best fitted model due to the highest values of R-2 and low values of chi(2), RMSE and RSS.