Drying of tomato slices: changes in drying kinetics, mineral contents, antioxidant activity and color parameters

The sun, oven (50 degrees C and 70 degrees C) and microwave oven (210 and 700 W) drying behaviors of tomato slices were investigated. Effects of these drying methods in terms of mineral content, antioxidant activity and color parameters of tomato slices were also studied. "Page, Modified Page and Midilli and Kucuk'' models exhibited generally high coefficient of determination (R-2) values ranging between 0.990 and 0.999, while two-term model fit better for sun drying. The calculated effective diffusivity (D-eff) values (m(2)/s) of tomato slices for the drying processes ranged between 0.24 and 111.13 x 10(-9). The concentrations (mg/kg dry matter) of major minerals such as K, Mg, Na, and P in dried tomato slices varied between of 31567-38003, 1183-1419, 822-1927, and 3256-4999, respectively. Microwave oven-dried (700 W) samples revealed better a* and b* color values than the other dried samples. Fresh and oven-dried (50 degrees C) samples exhibited the lowest trolox equivalent antioxidant capacity (TEAC) and 2,2-diphenyl-1-picrylhydracyl (DPPH) radical scavenging activities.