Microwave-vacuum drying effect on drying kinetics, lycopene and ascorbic acid content of tomato slices

Abstract

This study investigated the microwave-vacuum drying on the drying kinetics and quality attributes of dried tomatoes such as lycopene and ascorbic acid contents. Among the thirteen thin layer drying models that were used to fit the experimental data, the Midilli et al gave the highest correlation coefficient, lowest residual sum of squares, root mean square error, and reduced chi-square, thus indicating that the model of Middilli et al best described the microwave-vacuum drying of tomato slices. The highest ascorbic acid retention occurred in the samples dried at 200 W and 0.06 MPa, with a significant decrease (p<0.05) from an initial mean value of 2.74 ± 0.29 to 1.87 ± 0.13 mg/g dry matter, representing a decrease of about 32% in relation to the fresh tomato. On the other hand, the lycopene content of the dried tomatoes significantly (p<0.05) increased from 2.96 mg/100 g dry matter to a maximum value of 25.44 mg/100 g dry matter after microwave-vacuum drying at 700 W and 0.04 MPa.