Air-impingement jet drying at high temperature and air velocity enhanced the dehydration efficiency, quercetin content, and antiradical properties of fig slices

Abstract

Drying is an effective method for preserving figs. Air-impingement jet drying (AIJD) and hot-air drying (HAD) were applied to investigate the effect of drying methods on the drying kinetics, polyphenol constituents, and antiradical properties of fig slices. Results showed that AIJD was more effective than HAD in decreasing drying time and protecting the 1,1-diphenyl-2-picrylhydrazyl (DPPH·) scavenging activity of the fig slices. Additionally, AIJD was used to dry the fig slices at different temperatures (40, 50, 60, 70, and 80°C) and air velocities (6, 7, and 8 m/s). The drying rates (DR) and effective moisture diffusivities (Deff) of the fig slices increased with the AIJD drying temperature. The AIJD drying activation energy (Ea) of the fig slices determined by the Arrhenius equation was 21.66 kJ/mol. The Page model was used to describe and predict the dehydration behaviour of the fig slices during AIJD. UHPLC-QqQ-MS/MS analysis identified seven phenolic acids and nine flavonoids in the dried fig slices, with quinic acid, rutin, and chlorogenic acid being the primary polyphenols. AIJD at 80°C and 8 m/s induced the highest 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS·+) scavenging activity and quercetin content in the fig slices than the other treatments.