Abstract
Refractance Window (RW) drying is a modern technique for producing dried powders, slices, or leathers from fruits and vegetables. This study evaluated the effects of temperature (60, 70, and 80 °C) and citric acid (CA) pretreatment (0.5, 1, and 1.5%) on the drying behavior, mass transfer, quality, and structural properties of RW-dried dragon fruit slices. Drying time at 80 °C was reduced by 36-63% with CA pretreatment. The Page model best described the drying kinetics, with high R(2) and low RMSE and chi-square values at 70 °C. CA pretreatment reduced external resistance and enhanced moisture transfer, as shown by microscopic analysis. Dragon fruit slices with 1.5% CA had the highest total phenolics and antioxidant activity. FTIR and XRD spectra confirmed structural changes, while microscopy revealed surface disruption and pore formation. Higher temperature and CA pretreatment improved drying efficiency and quality retention in RW-dried dragon fruit slices. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10068-025-01909-9.