Characteristics and multi-objective optimization of carrot dehydration in a hybrid infrared /hot air dryer

Abstract

As the main drying systems used in different industries, convective dryers are associated with some elementary shortcomings. Combination of the systems and infrared power could result in shorten the process time, uniform heating, efficient energy consumption, and high-quality dried products. In this study, 3 mm carrot slices were dried by practicing different air temperatures, infrared powers and irradiation distances. Response surface methodology was also used to optimize the process variables. The average diffusivity varied in the range of 2.01 × 10−10–12.10 × 10−10 m2/s. The consumed specific energy changed from 30.20 to 87.51 MJ/kg. Shrinkage of the carrots was in the range of 23.49–51.25%. The range of rehydration ratio and total color change of the dried carrots was 4.71–9.01 and 15.25–33.17, respectively. The antioxidant activity and total phenolic content were found to be varied from 60.07 to 89.57% and from 26.59 to 42.65 mg GA/10 g dry matter, respectively. Designating by desirability function of about 0.89, the optimized control factors were determined to be 73.3 °C air temperature, 720 W infrared power and 7 cm irradiation distance.