Impact of process parameters on drying behaviour, mass transfer and quality profile of refractance window dried banana puree

Refractance Window (RW) is a relatively new drying technique for producing dried powders, slices or leathers from fruits and vegetables. In the present study, the effect of temperature (70, 80 and 90 °C) and thickness of puree (2 and 3 mm) on drying characteristics, mass transfer and quality attributes of RW dried banana puree were investigated. Results showed that drying at 90 °C reduced drying time (~61–64%) and energy consumption (~30–44%), as compared to drying at a lower temperature (70 °C) for both the thickness. The effective diffusion coefficient (Deff) values obtained (2.89 × 10−9 to 8.84 × 10−9 m2/s) using Dincer and Dost analytical approach had higher R2 (0.980–0.991) and lower RMSE (0.029–0.053) values. RW drying at 90 °C resulted in higher ascorbic acid retention (~76–78%) with the least total colour change (3.4–6.9) compared to other studied conditions. Besides, retention of total phenolic (10.3 mg GAE/g dm) and flavonoid contents (3.4 mg QE/g dm), as well as antioxidant capacity (58.8 mM TE/g dm), were also better in samples dried at 90 °C. The study suggested that drying at a higher temperature during RW not only reduces drying time but also improves retention of quality attributes.