Catalytic Infrared Drying Effect on Tomato Slices Properties

Abstract

In this study, the effect of distance between Far-Infrared Radiation (FIR) emitter and the surface of tomato slices and sample thickness on drying time, non-enzymatic browning, brightness, the ratio of redness to yellowness, ascorbic acid content, and lycopene content of the dried tomato slices was investigated. Three levels of distance (38 to 50 cm), sample thickness (7 to 11 mm) were used for the experiment. The desirability index technique was used to determine the ideal drying conditions that yield minimum drying time and non-enzymatic browning and maximum brightness color, redness to yellowness ratio, lycopene content, and ascorbic acid of drying of tomato slices. At the best conditions of 40.29 cm distance and 9.04 mm sample thickness, the drying time was 108 ± 4 minutes; the non-enzymatic browning index was 0.338 ± 0.12 Abs unit; the brightness was 40.43 ± 2.29; the ratio of redness to yellowness was 0.92 ± 0.13; the ascorbic acid content was 3.76 ± 0.27 mg/g dry matter; and the lycopene content was 72.34 ± 19.87 mg/100 g dry matter. These results demonstrate that FIR should be considered as an efficient drying method for tomato with respect to colour and ascorbic acid preservation, minimization of brown pigment formation and increment in lycopene content.