Modeling of moisture loss kinetics and color changes in the surface of lemon slice during the combined infrared-vacuum drying

Abstract

Color is one of the most important appearance attributes of food materials, since it influences consumer acceptability. In this study the effects of combined infrared-vacuum drying on the drying kinetics, moisture diffusivity, surface changes (shrinking) and color changes kinetics of lemon slices were investigated. Both the infrared lamp power and vacuum pressure influenced the drying time of lemon slices. The regression results showed that the quadratic model satisfactorily described the drying behavior of lemon slices with highest R value and lowest SE values. The effective moisture diffusivity increased from 2.92 × 10−10 and 1.58 × 10−9 m2/s when the infrared lamp power was increased from 300 to 400 W. The colour parameters L∗ (lightness), a∗ (redness/greenness), b∗ (yellowness/blueness), and ΔE (total colour difference) were used to estimate colour changes during drying. L∗, a∗ and b∗ values of dried lemon increased during drying. The rise in infrared power has a negative effect on the ΔE and with the increase of infrared radiation power it was increased. Different kinetic models were used to fit the experimental data and the results revealed that the power model was the most suitable to describe the color change intensity (ΔE).