Thin layer drying models, antioxidative activity and phenolic compounds of rose petals (Rosa damascena Mill.) in tray dryer

Abstract

The drying behavior of the Damask rose (Rosa damascena Mill.) petals in a thin layer hot air drying at 35, 45 and 55°C and 0.4, 1.2 and 2 (m·s-1) air velocity levels, was investigated. The Midilli was the most suitable model among 14 different thin-layer models for showing the thin-layer drying characteristics. At the experimental temperature (35-55°C) and air velocity levels (0.4, 1.2 and 2 m·s-1) the effective moisture diffusivity was 2.02×10-12- 11.3×10-12 (m2·s-1) and the activation energy varied from 56.3 to 64.5 (kJ·mol-1). Total anthocyanin content (TAC) ranged 77-240 (mg·L-1). The rose petal extracts showed higher DPPH (59.51%) and lower FRAP (1213.24 μmol(Fe+2)·L-1), at an increasing temperature from 35 to 55°C. Results showed that the higher temperature caused less TAC. At 45-55°C and air velocities 0.4-1.2 (m·s-1) the number of anthocyanins increased significantly, but at air velocities, 1.2- 2 (m·s-1) a decrease was observed.