Mass transfer and color change kinetics of infrared drying of rose petals and its impact on physico‐chemical properties

Abstract

The present study investigated the effects of infrared and forced convective air at different infrared power levels (300, 400, and 500 W) and hot air temperatures (50, 57, and 65°C) on thin layer drying of rose petals. Infrared drying requires 50%–52% less time as compared with forced convective drying. The initial and final moisture content of rose petals were 84% (w.b.) and 4.5% (w.b.) respectively. The Midilli–Kucuk model gives a superior fit for both the drying methods followed by Avhad and Marchetti, and the Page model. The zero‐order, followed by the first‐order color kinetics model gives the best fitting for L*, a*, and b* values. Moisture diffusivity was increased by infrared power (1.7308 × 10−8 to 4.1495 × 10−8 m2/s) and hot air temperature (9.3715 × 10−9 to 1.1709 × 10−8 m2/s). The activation energy obtained for rose petals in hot air dryers and infrared dryers was 51.09 kJ/mol and 6.50 kW/kg, respectively. Samples dried at 500 W infrared drying for 18 min demonstrated higher retention of color, ascorbic acid (61.03 ± 2.6 mg/100 g), and anthocyanin content (295.75 ± 65.70 mg/100 g) in the rose petals. Practical Applications Several drying techniques are available, though continuous efforts have been made to improve drying methods in terms of energy efficiency and product quality attributes. The present work has been carried out considering the dearth of information on the influence of infrared power/intensity on drying behavior and product quality of rose petals. Mass and color kinetics has been studied for a better understanding of the process along with rehydration, ascorbic acid and anthocyanin content. Our results showed that the infrared drying has significant industrial importance as it provides an efficient way to dry flowers, preserving their quality and extending their shelf life.